Forum Firefox issue
Well, it's nothing to do with Firefox unless you changed its settings to something odd. I use Firefox 4 and am having no problems.
Maybe remove and reinstall?
Don't count your weasels before they pop dink!
I'd try running "Firefox (Safe Mode)" from your start menu to disable all plugins and test it before re-installing the whole thing. Lots of people add plugins because they do awesome things, and then ya find one that accidentally bugs a core component of the browser haha.
If you have skype installed on your computer disabling that plugin tends to be a must; it tends to break things last I heard, and it's only really useful for people with a subscription to landline calling anyway.

10 50's To Date! Check out Titan Sentinel; it got my CoH presence synced online

Not that it has anything to do with this topic, but I have to disagree. The free Skype calls are almost a daily thing for me and my friends while playing CoH in lieu of using Ventrilo/Teamspeak.
@Sparky Jenkins || Freedom Server | Union Server
Main Hero: Inferno Sparky - Fire/Fire Blaster
Main Villain: Kerry Astrid - Fire/Cold Corruptor
Yeah, the app is great, I just mean the firefox plugin.

10 50's To Date! Check out Titan Sentinel; it got my CoH presence synced online

When I enter the text in the main body and hit submit, the test is all deleted and I get the message about needing a certain number of characters to submit a message. When I hit the back button, the main text body is still empty. The Title block stays filled both times. This is with Firefox 4 on Win7. I logged out, cleared all my cookies, logged back in and tried again, and still no luck.
Everything works fine using IE9, though.
edit: I tried to edit this post using Firefox and when I hit submit, the original message I posted in IE9 was still there, but none of the changes I made with Firefox showed up. This edit paragraph and the edits in the original paragraph are made with IE9.