I'll add a little more info here.
The problem is in message 246. I determined this by starting an administrator edit on several messages, which displays that single message above the edit screen.
Message 246 displays far too wide. (I did not save my "edit" results).
In message 246, there is a paragraph that begins with the sentence "But we don't know what the fraction was for homozygous versus heterozygous." (without the quotes). That paragraph shows up as 7 lines in the edit window, 4 lines on my firefox display. IE is attempting to display that as one very long line. I was unable to find a reason for this, except a possible bug in IE.
I wonder what IE7 does with that line