I have a user who clicks the calendar control and no drop-down appears. He is using Firefox 3.6, and I was using 3.5.7. I had no issues. I then upgraded Firefox to 3.6 and am now having the same problem.
I'll create a ticket, but I'm curious if anyone else has noticed this.
I have some of the same issues with the UltraWebGrid, I can click a row and a .flv will play on an embedded player, this used to work in Firefox 3.5 but does not work on Firefox 3.6.