I implemented a little Linq in an existing website that uses LLBLGen, on a shared host with pretty tight security, and got the error:
That assembly does not allow partially trusted callers.
By backing out the Linq code and removing the reference to SD.LLBLGen.Pro.LinqSupportClasses.NET35.dll the error went away.
It's pretty reproducible(did it twice). Is there something about the LinqSupportClasses assembly? Is it not signed? The assembly is marked as 2.6.08.1219.