VS 2012 - referenced assemblies occasionally missing

Hello all,

I have a strange problem. Once in a while Visual Studio 2012 forgets to include certain assemblies (always Codeplex ImageTools) during Silverlight application build. Assemblies are properly referenced and used.

It seems to be completely nondeterministic.

I really know the basics. I have been using Visual Studio since the very first version (over 12 years).

Any ideas? Did anyone experienced a similar issue?
It started after migrating the project from VS 2010.

Thanks,

Thomas