class A : A
{
   public override void Foo() { }
}

Put the caret onto 'override' keyword. Resharper hangs.
Call stack from CLRDbg:

[External Code]
> JetBrains.ReSharper.Util.dll!JetBrains.ReSharper.Util.WeakToStrongHashtable.WeakReferencesComparer.Compare(object x = {JetBrains.ReSharper.Util.EquableWeakReference}, object y = {JetBrains.ReSharper.Psi.CSharp.Impl.Tree.SimpleReferenceName}) Line 23 + 0x7 bytes C#
[External Code]
JetBrains.ReSharper.Util.dll!JetBrains.ReSharper.Util.WeakToStrongHashtable.this[object].get(object key = {JetBrains.ReSharper.Psi.CSharp.Impl.Tree.SimpleReferenceName}) Line 57 + 0xa bytes C#
JetBrains.ReSharper.Psi.dll!JetBrains.ReSharper.Psi.Impl.Resolve.ResolveCache.this[JetBrains.ReSharper.Psi.ExtensionsAPI.Resolve.IRef].get(JetBrains.ReSharper.Psi.ExtensionsAPI.Resolve.IRef reference = {JetBrains.ReSharper.Psi.CSharp.Impl.Tree.SimpleReferenceName}) Line 46 + 0x10 bytes C#
JetBrains.ReSharper.Psi.dll!JetBrains.ReSharper.Psi.Impl.Resolve.ResolveUtil.ResolveWithCache(JetBrains.ReSharper.Psi.ExtensionsAPI.Resolve.IInternalRef reference = {JetBrains.ReSharper.Psi.CSharp.Impl.Tree.SimpleReferenceName}) Line 582 + 0xd bytes C#
JetBrains.ReSharper.Psi.dll!JetBrains.ReSharper.Psi.CSharp.Impl.Tree.ReferenceName.Resolve() Line 192 + 0x8 bytes C#
JetBrains.ReSharper.Psi.dll!JetBrains.ReSharper.Psi.TypeFactory.CreateType(JetBrains.ReSharper.Psi.CSharp.IReferenceNameNode referenceName = {JetBrains.ReSharper.Psi.CSharp.Impl.Tree.SimpleReferenceName}) Line 90 + 0xa bytes C#
JetBrains.ReSharper.Psi.dll!JetBrains.ReSharper.Psi.TypeFactory.CreateType(JetBrains.ReSharper.Psi.CSharp.IDeclaredTypeUsageNode typeUsage = {JetBrains.ReSharper.Psi.CSharp.Impl.Tree.UserDeclaredTypeUsageStub}) Line 109 + 0x1d bytes C#
JetBrains.ReSharper.Psi.dll!JetBrains.ReSharper.Psi.CSharp.Impl.Tree.ClassLikeDeclarationBase.SuperTypes.get() Line 100 + 0x1b bytes C#
JetBrains.ReSharper.Psi.dll!JetBrains.ReSharper.Psi.CSharp.Impl.Cache2.CSharpClassLikeTypeElement.GetSuperTypes() Line 183 + 0x9 bytes C#
JetBrains.ReSharper.Psi.dll!JetBrains.ReSharper.Psi.CSharp.Impl.Cache2.CSharpClass.GetSuperTypes() Line 55 + 0x8 bytes C#
JetBrains.ReSharper.Psi.dll!JetBrains.ReSharper.Psi.CSharp.Impl.Cache2.CSharpClass.GetSuperClass() Line 27 + 0x7 bytes C#
JetBrains.ReSharper.Daemon.CSharp.dll!JetBrains.ReSharper.Daemon.CSharp.QuickFixes.QuickFixUtil.FindBaseOverridableMember(JetBrains.ReSharper.Psi.ITypeElement typeElement = {JetBrains.ReSharper.Psi.CSharp.Impl.Cache2.CSharpClass}, JetBrains.ReSharper.Daemon.CSharp.QuickFixes.QuickFixUtil.TestOverridable test = {JetBrains.ReSharper.Daemon.CSharp.QuickFixes.QuickFixUtil.TestOverridable}) Line 27 + 0x44 bytes C#
JetBrains.ReSharper.Daemon.CSharp.dll!JetBrains.ReSharper.Daemon.CSharp.QuickFixes.FixSignatureFix.FindOwner(out JetBrains.ReSharper.Psi.Resolve.ISubstitution substitution = null) Line 77 + 0x28 bytes C#
JetBrains.ReSharper.Daemon.CSharp.dll!JetBrains.ReSharper.Daemon.CSharp.QuickFixes.FixSignatureFix.IsAvailableEx() Line 31 + 0x1b bytes C#
JetBrains.ReSharper.Daemon.CSharp.dll!JetBrains.ReSharper.Daemon.CSharp.QuickFixes.FixBase.IsAvailable() Line 29 + 0x19 bytes C#
JetBrains.ReSharper.Daemon.dll!JetBrains.ReSharper.Daemon.Impl.QuickFixTableImpl.CreateQuickFixes(JetBrains.ReSharper.Daemon.IHighlighting highlighting = {JetBrains.ReSharper.Daemon.CSharp.Stages.NoSuitableMemberForOverrideError}) Line 86 + 0xf bytes C#
JetBrains.ReSharper.Daemon.dll!JetBrains.ReSharper.Daemon.Impl.BulbManagerImpl.GetAvailableActions(JetBrains.ReSharper.TextControl.ITextControl textControl = {JetBrains.VSAddin.TextControl.VSTextControl}, int offset = 27, bool canShowPopup = true, bool canShowQuickFixes = true, out JetBrains.ReSharper.Util.TextRange popupRange = {JetBrains.ReSharper.Util.TextRange}) Line 256 + 0xe bytes C#
JetBrains.ReSharper.Daemon.dll!JetBrains.ReSharper.Daemon.Impl.BulbManagerImpl.ShowIndicator(bool canShowPopup = true) Line 162 + 0x46 bytes C#
JetBrains.ReSharper.Daemon.dll!JetBrains.ReSharper.Daemon.Impl.BulbManagerImpl.OnTimer() Line 138 + 0xd bytes C#
JetBrains.ReSharper.Shell.dll!JetBrains.ReSharper.Shell.Invocator.PendingAction.Execute() Line 233 + 0xe bytes C#
JetBrains.ReSharper.Shell.dll!JetBrains.ReSharper.Shell.Invocator.ProcessQueue() Line 165 + 0xb bytes C#
[External Code]