I have the same problem and more!
When I try to write a new post (/wp-admin/post-new.php) using Firefox, the compose layout is a messy. The problem does not happen using IE.
Proof(firefox): https://img384.imageshack.us/img384/7631/prooffffn8.jpg
Proof(IE): https://img67.imageshack.us/img67/9536/proofierd1.jpg
As tou can see, the layout using Firefox is completely broken! What’s going on???
HELP!!!
Windows Vista: FF3 – not working // IE – working
Ubuntu: FF3 – not working