I am getting following error at run-time "Loading this assembly would produce a different grant set from other instances" when calling a vb.net 1.1 assembly from a ASP.net 2.0 website. Any idea what could be the reason behind this error?

The scenario is :

There is one web application which is built as WebSite in ASP.NET 2.0. The webpages in this website loads a 2.0 vb.net assembly, which inturn to load a 1.1 vb.net assembly.

The code is failing at run time, in loading the assembly of 1.1 dll. Please help.