Can't Add New Folders, Code, etc. After Update to Xamarin Studio 4.0.12 (build 3)

Yikes! This version is disastrous for me on a Mac. Any attempt to add anything new or edit a file fails with an error message like this:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> MonoDevelop.VersionControl.Subversion.SubversionException: '/Users/kmullins/Projects/ActionPack/ActionPack.iOS/New Folder' is not a working copy at MonoDevelop.VersionControl.Subversion.Unix.SvnClient.CheckError (IntPtr error, Nullable

1 allowedError) [0x000aa] in /Users/builder/data/lanes/monodevelop-lion-monodevelop-4.0.12-branch/593d7acb/source/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl.Subversion.Unix/MonoDevelop.VersionControl.Subversion.Unix/SvnClient.cs:50 
  at MonoDevelop.VersionControl.Subversion.Unix.SvnClient.CheckError (IntPtr error) [0x0000b] in /Users/builder/data/lanes/monodevelop-lion-monodevelop-4.0.12-branch/593d7acb/source/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl.Subversion.Unix/MonoDevelop.VersionControl.Subversion.Unix/SvnClient.cs:26 
  at MonoDevelop.VersionControl.Subversion.Unix.UnixSvnBackend.CheckError (IntPtr error) [0x00001] in /Users/builder/data/lanes/monodevelop-lion-monodevelop-4.0.12-branch/593d7acb/source/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl.Subversion.Unix/MonoDevelop.VersionControl.Subversion.Unix/SvnClient.cs:173 
  at MonoDevelop.VersionControl.Subversion.Unix.UnixSvnBackend.Status (MonoDevelop.VersionControl.Repository repo, FilePath path, MonoDevelop.VersionControl.Subversion.SvnRevision rev, Boolean descendDirs, Boolean changedItemsOnly, Boolean remoteStatus) [0x00077] in /Users/builder/data/lanes/monodevelop-lion-monodevelop-4.0.12-branch/593d7acb/source/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl.Subversion.Unix/MonoDevelop.VersionControl.Subversion.Unix/SvnClient.cs:511 
  at MonoDevelop.VersionControl.Subversion.SubversionBackend.GetDirStatus (MonoDevelop.VersionControl.Repository repo, FilePath localPath, Boolean getRemoteStatus) [0x0002b] in /Users/builder/data/lanes/monodevelop-lion-monodevelop-4.0.12-branch/593d7acb/source/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl.Subversion/MonoDevelop.VersionControl.Subversion/SubversionVersionControl.cs:147 
  at MonoDevelop.VersionControl.Subversion.SubversionBackend.GetVersionInfo (MonoDevelop.VersionControl.Repository repo, FilePath localPath, Boolean getRemoteStatus) [0x00015] in /Users/builder/data/lanes/monodevelop-lion-monodevelop-4.0.12-branch/593d7acb/source/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl.Subversion/MonoDevelop.VersionControl.Subversion/SubversionVersionControl.cs:109 
  at MonoDevelop.VersionControl.Subversion.SubversionRepository+<OnGetVersionInfo>c__Iterator0.MoveNext () [0x00079] in /Users/builder/data/lanes/monodevelop-lion-monodevelop-4.0.12-branch/593d7acb/source/monodevelop/main/src/addins/VersionControl/MonoDevelop.VersionControl.Subversion/MonoDevelop.VersionControl.Subversion/SubversionRepository.cs:96 
  at System.Collections.Generic.List

1[MonoDevelop.VersionControl.VersionInfo].AddEnumerable (IEnumerable

1 enumerable) [0x00013] in /private/tmp/source/bockbuild-xamarin/profiles/mono-mac-xamarin-no-pcl/build-root/mono-3.2.0/mcs/class/corlib/System.Collections.Generic/List.cs:134 
  at System.Collections.Generic.List

1[MonoDevelop.VersionControl.VersionInfo]..ctor (IEnumerable

1 collection) [0x0002f] in /private/tmp/source/bockbuild-xamarin/profiles/mono-mac-xamarin-no-pcl/build-root/mono-3.2.0/mcs/class/corlib/System.Collections.Generic/List.cs:69 
  at System.Linq.Enumerable.ToList[VersionInfo] (IEnumerable

1 source) [0x00006] in /...

And this is on a project that has never been under version control! Rolling back to 4.0.10 now...