I'm getting a Specified cast is not valid error. What does this mean?

Pre Beta 1

""In Pre-Beta 1 drops, the ResolveAssemblyReference task would occasionally throw this error when attempting to read in the cache file"" ResolveAssemblyReference.cache. The exact cause is unknown, but likely has to do with the existence of a ResolveAssemblyReference.cache file that was written using a different drop of the .NET Framework than the one currently being used to read it back.

The workaround is to delete the ResolveAssemblyReference.cache file from your obj\debug and obj\release directories, and try building again.

Beta 1 and Beyond

This issue has been fixed. If you see it please send mail to MSBuild@microsoft.com