This has been reported in 1.0.18.6 and 2.0.0.0. It's likely due to 7a88701

Microsoft.VisualStudio.Composition.CompositionFailedException: An exception was thrown while initializing part "GitHub.VisualStudio.TeamExplorer.Connect.GitHubConnectSection0". ---> System.Windows.Markup.XamlParseException: Set property 'GitHub.VisualStudio.Helpers.SharedDictionaryManager.Source' threw an exception. ---> System.IO.FileNotFoundException: Could not load file or assembly 'GitHub.UI, Culture=neutral' or one of its dependencies. The system cannot find the file specified.
   at System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
   at System.Reflection.RuntimeAssembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
   at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
   at System.Reflection.Assembly.Load(AssemblyName assemblyRef)
   at System.Windows.Navigation.BaseUriHelper.GetLoadedAssembly(String assemblyName, String assemblyVersion, String assemblyKey)
   at MS.Internal.AppModel.ResourceContainer.GetResourceManagerWrapper(Uri uri, String& partName, Boolean& isContentFile)
   at MS.Internal.AppModel.ResourceContainer.GetPartCore(Uri uri)
   at System.IO.Packaging.Package.GetPartHelper(Uri partUri)
   at System.IO.Packaging.Package.GetPart(Uri partUri)
   at System.IO.Packaging.PackWebResponse.CachedResponse.GetResponseStream()
   at System.IO.Packaging.PackWebResponse.GetResponseStream()
   at System.IO.Packaging.PackWebResponse.get_ContentType()
   at MS.Internal.WpfWebRequestHelper.GetContentType(WebResponse response)
   at MS.Internal.WpfWebRequestHelper.GetResponseStream(WebRequest request, ContentType& contentType)
   at System.Windows.ResourceDictionary.set_Source(Uri value)
   at GitHub.VisualStudio.Helpers.SharedDictionaryManager.set_Source(Uri value) in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\common\SharedDictionaryManager.cs:line 54
   --- End of inner exception stack trace ---
   at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri)
   at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri)
   at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream)
   at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
   at GitHub.VisualStudio.UI.Views.GitHubConnectContent.InitializeComponent() in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\GitHub.VisualStudio.UI\UI\Views\GitHubConnectContent.xaml:line 1
   at GitHub.VisualStudio.UI.Views.GitHubConnectContent..ctor() in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\GitHub.VisualStudio.UI\UI\Views\GitHubConnectContent.xaml.cs:line 16
   at GitHub.VisualStudio.TeamExplorer.Connect.GitHubConnectSection.OnPropertyChange(Object sender, PropertyChangedEventArgs e) in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\GitHub.TeamFoundation.14\Connect\GitHubConnectSection.cs:line 198
   at GitHub.Primitives.NotificationAwareObject.RaisePropertyChanged(String propertyName) in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\GitHub.Exports\Helpers\NotificationAwareObject.cs:line 12
   at GitHub.VisualStudio.Base.TeamExplorerItemBase.set_IsVisible(Boolean value) in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\GitHub.VisualStudio.UI\Base\TeamExplorerItemBase.cs:line 141
   at GitHub.VisualStudio.TeamExplorer.Connect.GitHubConnectSection.Refresh(IConnection connection) in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\GitHub.TeamFoundation.14\Connect\GitHubConnectSection.cs:line 160
   at GitHub.VisualStudio.TeamExplorer.Connect.GitHubConnectSection.UpdateConnection() in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\GitHub.TeamFoundation.14\Connect\GitHubConnectSection.cs:line 190
   at GitHub.VisualStudio.TeamExplorer.Connect.GitHubConnectSection..ctor(ISimpleApiClientFactory apiFactory, ITeamExplorerServiceHolder holder, IConnectionManager manager, IPackageSettings packageSettings, Int32 index) in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\GitHub.TeamFoundation.14\Connect\GitHubConnectSection.cs:line 108
   at GitHub.VisualStudio.TeamExplorer.Connect.GitHubConnectSection0..ctor(ISimpleApiClientFactory apiFactory, ITeamExplorerServiceHolder holder, IConnectionManager manager, IPackageSettings settings) in Y:\jenkins\workspace\GitHub for Visual Studio speakeasy jenkinskeep\src\GitHub.TeamFoundation.14\Connect\GitHubConnectSection0.cs:line 21
   --- End of inner exception stack trace ---
   at Microsoft.VisualStudio.Composition.RuntimeExportProviderFactory.RuntimeExportProvider.RuntimePartLifecycleTracker.CreateValue()
   at Microsoft.VisualStudio.Composition.ExportProvider.PartLifecycleTracker.Create()
   at Microsoft.VisualStudio.Composition.ExportProvider.PartLifecycleTracker.MoveNext(PartLifecycleState nextState)
   at Microsoft.VisualStudio.Composition.ExportProvider.PartLifecycleTracker.MoveToState(PartLifecycleState requiredState)
   at Microsoft.VisualStudio.Composition.ExportProvider.PartLifecycleTracker.GetValueReadyToExpose()
   at Microsoft.VisualStudio.Composition.ExportProvider.<>c__DisplayClass53_0.<CreateExport>b__0()
   at Microsoft.VisualStudio.Composition.ExportProvider.<>c__DisplayClass55_0.<CreateExportFactoryExport>b__1()
   at Microsoft.VisualStudio.Composition.ExportProvider.<>c__DisplayClass54_0.<CreateExportFactory>b__0()
   at Microsoft.VisualStudio.Composition.DelegateServices.<>c__DisplayClass2_0`1.<As>b__0()
   at System.ComponentModel.Composition.ExportFactory`1.CreateExport()
   at Microsoft.VisualStudio.Composition.NetFxAdapters.MefV1ExportProvider.ComposablePartDefinitionForExportFactory.CreatePart()
   at System.ComponentModel.Composition.ReflectionModel.ExportFactoryCreator.LifetimeContext.GetExportLifetimeContextFromExport[T](Export export)
   at System.ComponentModel.Composition.ReflectionModel.ExportFactoryCreator.<>c__DisplayClass6_0`2.<CreateStronglyTypedExportFactoryOfTM>b__0()
   at System.ComponentModel.Composition.ExportFactory`1.CreateExport()
   at Microsoft.TeamFoundation.Controls.WPF.TeamExplorer.Framework.TeamExplorerSectionHost.Create()

Currently, our Beta version crashes the Team Explorer pane when a user logs in, perform no action in Visual Studio, closes app and relaunches app.

Steps to Reproduce

• Launch Microsoft Visual Studio and connect to GitHub from the Team Explorer
• Sign in with valid credentials.
• No project added prior or cloned.
• Close Visual Studio app without signing out.
• Relaunch Visual Studio

Expected result - Visual Studio should launch with user's GitHub account already connected in Team Explorer.
Actual result - Visual Studio launches with error messages in Team Explorer.

GitHub Extension 2.0 Beta Version.
OS - Windows 10
Microsoft Visual Studio Enterprise 2015
Version 14.0.25424.00

Screenshot is as seen above.