I've never needed to work with Track Changes, so I don't know if it's likely to be any part of the cause, but in gneral, when some part of the program stops working as expected, it's either user error, a bug, or currupt preferences. I can't help with the first two, but here's a link to how to fix bad prefs: Replace Your Preferences
Also, be sure you've installed the 7.5.2 patch.
You've probably already looked at this, but is your cursor in a story when you try to open the Story Editor panel?
Interesting - I tried that yesterday and it didn't work. Tried it again today (i.e., made sure that the cursor was in the story) and it worked. I was also having trouble scrolling down through the story editor through the successive panels. I had to click the panel outside of story editor, and then click Control + Y to get the story editor in the right place. I'm a newbie and used to working in Word, so this will take some getting used to. Thanks to your and Peter for your replies!