MonoDevelop (Mac OS X): Git Add-In crashes

My MonoDevelop crashes when I click on "Changes"-Button.

This is the crash log:

NGit.Errors.MissingObjectException: Missing unknown f223c41a3ed4fef41853d046263c5fc56a4f9de9 at NGit.Storage.File.WindowCursor.Open (NGit.AnyObjectId objectId, Int32 typeHint) [0x0005b] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/external/ngit/NGit/NGit.Storage.File/WindowCursor.cs:130 at NGit.ObjectReader.Open (NGit.AnyObjectId objectId) [0x00000] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/external/ngit/NGit/NGit/ObjectReader.cs:229 at NGit.Revwalk.RevWalk.ParseAny (NGit.AnyObjectId id) [0x00013] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/external/ngit/NGit/NGit.Revwalk/RevWalk.cs:943 at NGit.Revwalk.RevWalk.ParseCommit (NGit.AnyObjectId id) [0x00000] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/external/ngit/NGit/NGit.Revwalk/RevWalk.cs:845 at MonoDevelop.VersionControl.Git.GitRepository.GetHeadCommit (NGit.Repository repository) [0x0001b] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl.Git/MonoDevelop.VersionControl.Git/GitRepository.cs:151 at MonoDevelop.VersionControl.Git.GitRepository.GetBaseText (FilePath localFile) [0x00000] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl.Git/MonoDevelop.VersionControl.Git/GitRepository.cs:139 at MonoDevelop.VersionControl.Views.DiffView.get_Control () [0x0001c] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl/MonoDevelop.VersionControl.Views/DiffView.cs:53 at MonoDevelop.Ide.Gui.SdiWorkspaceWindow+c_AnonStorey41.<>m_43 (System.Object sender, System.EventArgs e) [0x0000b] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/src/core/MonoDevelop.Ide/MonoDevelop.Ide.Gui/SdiWorkspaceWindow.cs:526 at MonoDevelop.Components.Tab.OnActivated (System.EventArgs e) [0x0000d] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/src/core/MonoDevelop.Ide/MonoDevelop.Components/Tabstrip.cs:342 at MonoDevelop.Components.Tab.set_Active (Boolean value) [0x00012] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/src/core/MonoDevelop.Ide/MonoDevelop.Components/Tabstrip.cs:233 at MonoDevelop.Components.Tabstrip.set_ActiveTab (Int32 value) [0x0002b] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/src/core/MonoDevelop.Ide/MonoDevelop.Components/Tabstrip.cs:62 at MonoDevelop.Components.Tabstrip.OnButtonPressEvent (Gdk.EventButton evnt) [0x0000b] in /BuildAgent/work/9ffd76bfa3f1a926/monodevelop/main/src/core/MonoDevelop.Ide/MonoDevelop.Components/Tabstrip.cs:148 at Gtk.Widget.buttonpressevent_cb (IntPtr widget, IntPtr evnt) [0x00000] in :0

Can you help me?