A while ago I asked about "DLL caused an exception" when calling a method that references another DLL. On that time I had no clues but now I think what may be causing the problem.
Assume I have an
System.Exception: Error while trying to call method X from DLL1.
---> System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
---> System.IO.FileLoadException: Could not load file or assembly 'DLL2', Version=2.1.5899, PublicKeyToken=null' or one of its dependencies. A strongly-named assembly is required.
a signed assembly cannot call an unsigned assembly. That's part of the trust chain and it does indeed mean you will have to sign all dependencies of your signed assembly.