When my mouse idles for a few minutes, I can't scroll with the keyboard with the up/down keys; it takes 5-15 sec. or I move my mouse and jumps to the right spot
This usually happens when I'm reading an article or tun away for a bit, but when I move my mouse again the page jumps down to the point it would have normally scrolled to.
I also notice that sometimes when I type in firefox, the cursor will take a few seconds to catch up as though the buffer were full, and I'm fairly sure I don't type thta fast.
EDIT: I've tested this and it doesn't happen in IE 8.
Wót Frankto
Wšykne wótegrona (1)
That can be caused by Firefox releasing memory and doing garbage collection.
If you start scrolling or moving the mouse on the page then Firefox needs to rebuild the DOM and that can take some time on complicated pages (e.g. tables or many nested elements).