This is a cross post from http://social.msdn.microsoft.com/Forums/en-US/vssetup/thread/ac890e5c-2de6-4526-86fb-9a3cd77ec80e as recommended from that thread.

Essentially running Visual Studio 2005 SP1 on Windows 7 x64 with a C# addin created (tried both any cpu and x32 configuration settings) will cause VS to crash at the end of the intellisense scan of a C++ project (even with intellisense disabled this still occurs).  This does not happen in VS 2008 (unfortunately we can't upgrade at present as we are too close to shipping).  Even an incredibly basic C# addin (as described in the other thread) triggers this behaviour.