I used both, IE and Firefox. I had no orange boxes on either browsers until yesterday, and they appeared in both browsers.
The problem with Firefox is that it doesn't like the cookie set by these boards, and I can't stay logged on. Minor annoyance.
IE is still a major security hole, as proven by the guy sitting next to me at work, who browse without being careful and gets about 2000 spywares a day and has to reinstall Windows every 2 months because the computer is beyond repair due to spywares.