I had a similar situation also for the first time. I had several tabs open and was dragging the favicon of this thread (http://www.ubuntuforums.org/showthread.php?t=22582) to a folder on the bookmark toolbar and Firefox start useing all CPU power. The cursor was showing the + sign and the whole system was not responding until Firefox crashed and the Problem Report dialog appeard.
** Attachment added: "firefox froze when dragging bookmark icon to toolbar" http://librarian.launchpad.net/5077960/_usr_lib_firefox_firefox-bin.1000.crash -- firefox froze when dragging bookmark icon to toolbar https://launchpad.net/bugs/70411 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs