This has been annoying me both on my new install at home and at my new work. For some reason I have decided to put up with it until now. If you don't have the source code for something the debugger wants to dive into (could be for any reason, the core of the code we are working on at the moment is got from an Open Wrap package), Visual Studio can make an attempt to jump into the assembly instead.?
It's an easy fix to stop this annoying behaviour anyway.?
Tools->Options->Debugging->Enable address-level debugging->Show disassembly if source not available