Just tested it now seems to be working fine. You have to click the 'Quick reply to this message' next to the Quote button then you should be able to use quick reply posting.
Quick reply didn't work for me when I first logged in this morning (Firefox 1.5), but now it's working and I have no idea why. I didn't change any options or anything. Try clearing out your cache, Scanorama, and see if that works.
It didn't work for before or after the upgrade until I went and check my Javascript settings on my firefox 1.5 and realised that I have disabled all the shitz. NOw that I have enabled "disable or replace context menu" it seems working now. Have a try