http://blogs.msdn.com/jmstall/archive/2009/07/09/icustomqueryinterface-and-clr-v4.aspxCLR V4 fixes an issue with COM-interop that’s been bothering me for a while. The problem is that unless you’re using a PIA, you can often have either your caller or callee be managed code, but not both .  You can import the same COM-classic interfaceen-USCommunityServer 2.1 SP1 (Build: 61025.2)