Two days without an answer so I'll throw in/out some suggestions. It is my last day visiting this board due to the need to do other things. Naturally, clear you cache memory. In extreme situations, a long 'history' should be cleared too, but that causes loss of what sites you visited too. Make sure you haven't loaded the phony "your FF needs updating" update which appears on an orange screen when you really weren't expecting such a new tab. The last 2 releases have caused lag on my system, for unknown reasons, and while I noticed via process-explorer that TCP/IP connections to my modum were numerious, a FF document indicates that this is semi-normal. Do note that on my machine, perhaps ill machine, when I go to hotmail aka 'live' and get my email, I can not do anything while the advertisement on the right side of the screen is downloading. That and/or hotmail is establishing connects to skype and doing other things. Microsoft and google have programs available not to fix your machine but to track useage for advertising. Notice the dozens of URL's flashing on the bottom of your screen during a page load? And the ads are not static but continually download too, or videos. Much fault IMO lies with the web page owners who aren't concerned either. Use task monitor (control-shift-del) to see what processes are busy. I had a network program using half my CPU cycles. The cause and solution I gave someone worked, but I can not supply you with the link to that post. Oh, the choppyness is more noticable on my machines on some sites which never let you read the bottom of the page. Perhaps there is another question describing your situation on this web site. U and I know that sometimes an answer is just too hard to find.

I have Adblockplus, and I clear my history/cookies/caches around once a month or so.

The only updates that I allow to happen to Firefox are ones that prompt you when you click on the desktop icon to open it up.

I'm fairly sure this new update broke something, because the 'fly' scrolling is something I can do just fine in skype.