IBM DB2 - Operation could destabilize the runtime

Hi, I am writing a number of unit tests for an existing ASP.NET application which is being upgraded using VS2010 and .NET Framework 4, using Microsoft test framework and TypeMock Isolator 6.0.6.0.

The underlying database is DB2 (Client is v9.7.5) and when trying to fake a DB2 command object I get a "System.Security.VerificationException: Operation could destabilize the runtime" error when running the test.

After lots of playing around it turns out that even reducing the test method to one line....

DB2Command cmd = new DB2Command();

...the error is still raised, however if I disable Isolator the error disappears. Note also the test works fine using .NET 3.5 even with Isolator enabled.

Any ideas?

Thanks very much,
Andy