Schema Library Project fails on first run

I just installed WinFS for the first time. I installed Beta 1 Refresh on a
system with Whidbey RTM. I can't get any Schema Library Projects to compile;
Visual Studio gives me two errors:

1. A conflicting assembly for the task assembly C:\Program Files\Microsoft
SDKs\WinFS\bin\WinFSBuildTasks.dll" has been found at
"C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\mscorlib.dll".
2. The "RemoveNonSchemas" task has been declared or used incorrectly, or
failed during construction. Check the speling of the task name and the
assembly name.

I get these errors both with my own Schema Library Project and with the
sample projects included in the WinFS install. I can't find any other way to
generate custom schema DLLs, so I'm kind of dead in the water.

Known issue? Any workarounds? Thanks.

Andy