Problem with RSA.ImportParameters() under ASP .NET

I have a problem with some code in an assembly that use
If the assembly is used in a WinForm application it's fine, but I'm having
troubles when it's used in ASP .NET.

The code is something like this:
RSA rsa = RSA.Create ();
rsa.ImportParameters (param);

I know it has got something to do with the IIS user not having the same
access rights to key stores and files as a normal user.
Unfortunately I can't change the code (not my assembly), so can anyone tell
me what I can tweak on the PC to make this work?