I'd try:
1) Going to view and messing with: Full Screen, Page Style, and preferences.
2) Downloading a new theme and installing it. I know a friend who managed to fix a similar problem by installing a downloaded theme.

Have you tried dragging the window in different areas? (Just had to check, no offense.)
4) Clearing cookies, history, and resetting your advanced internet options.
Otherwise, re-installing is your best bet.
- SOup