VS 2003 .NET.
It only seems to happen when I copy some source code to the clipboard and then set a breakpoint in my clipboard application where I fetch the text using GetClipboardData:
OpenClipboard(hWnd);
HANDLE hData = GetClipboardData(CF_TEXT);
std::string s = (char*)GlobalLock(hData);
If I hover the mouse over 's', my source code gets colorized.
PS. It's really frustrating that you can't upload screenshots here...