With more and more browsers (Firefox, IE 7) now supporting tabs, can the Quick Reply button do something else than open another window? Some boards just open a space in the same space where you can type. I don't know anything about boards so I don't know it this is possible with this one, but the new window opening (which means navigating to a new tab) gets a little annoying.
I also use the latest version of firefox and it works fine for me. Try configuring your settings. BTW, no, you cannot upen a post window directly into the thread. That's neither our doingor a shortcoming with firefox, it is the design of the forum software.