Here's a flash screencast of me doing an edit first in IE7 without success and then without any problems in Mozilla.
I've also seen it partly where only some of the text I write is actually updated. Seems in IE7 it somehow cuts the edit sometimes fully or partially. Really strange. I've tried it on WinXP SP2 IE7 and Vista IE7 seems the same issue for me both places. If you can't reproduce it at your end it's very strange.