Q: All of a sudden my hotkeys aren't working. What's going on?

A: Check your caps lock. It sounds silly, but it happens to everyone. Hotkeys in Maya are case-sensitive. If that's not it, check the hotkey editor (Window > Settings/Preferences > Hotkey Editor) to see if somehow the hotkeys have actually been changed. You can also try deleting the userHotkeys.mel file in your prefs folder (usually in My Documents > maya > version ## > prefs). The default set of hotkeys will be regenerated when you re-open Maya.