Whenever I press Ctrl+Shift+A IE opens a popup window that says 'enter abbreviation', even when IE isn't open and I'm in a different program. My computer (Vista) has IE8 installed on it, but if fixing the problem means uninstalling it, that's fine.
I'm experiencing the same thing on my work computer. Nothing happens when I enter text and hit enter. The window just disappears.
/edit: Ha! It's from Notepad++. The Zen Coding plugin adds that popup, and Notepad++ doesn't appear to keep its hotkeys local.