I got your test PM, and I was able to attempt to reply, but when I clicked "Send", nothing happened. My version of Firefox is: 21.0 on this laptop, I'll check the version of Firefox on my other laptop when I get home, and tell you the version of IE I was using (I believe it's 8, possibly 9, but I don't think 9 is available on Windows XP).
Also, in Firefox 21.0, the only way I was able to see the "send" button was by tabbing through everything as the format was all jacked up.
Edited to add:
If I paid attention the URL, the forums are using phpBB3. Have you done any of the updates to the forum software? I know using a custom template is cause for concern to not update without doing so in a test environment as you don't want your databases to blow up, or have your entire forums go down, but if you want some help with troubleshooting and resolving any issues, I'd be more than happy to help.