I accidentally found this bug today. I was in TextEdit and hit my F11 (Exposé - Show Desktop) key by mistake when I was reaching for the Delete key. So I hit the F11 key again to bring back my work, and found out that if you hit the F11 key and then hit any qwerty keys (including the Delete key) it will affect any document, or even text input areas in a web browser.
I tested this in TextEdit, Safari, Adium, and Word on 10.5 and 10.4. So if you use F11, be careful not to press any qwerty keys while in that mode.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080131084518142