I think you are confusing Intellisense and Debugger DataTips.
I just did a quick test in a VC6 project built in VS 2010, and the VS 2010 debugger shows the members of std::vector correctly in the debugger. I suspect that you either have a corrupt installation, or your version of Visual Studio is not fully up to date. It's a long shot, but also make sure that you're not linking different versions of the STL libraries into the same executable.