Apparently my problem has gone away. Yesterday I tried to reply to a thread using the quote button and couldn't, then realized I couldn't reply in any fashion, even though I could start a thread. Very strange.
I could not reply to a post last night either, I tried to reply to your test and just sat here watching the screen. I could type without the source button but when I hit submit it would just show the wait screen. Last night tried on two different computers one with IE8 and one with IE6 with IE8.