I am running 64-bit Windows on an 2.2GHz 2nd generation i7 and 8GB of RAM.
When I first boot up, the RAM usage is 25-30%, which is reasonable, but after about two to four hours, it may go up to 70-80% with Firefox open, and then drop to about 65% when I close Firefox.
It won’t change even if I disconnect, only if I reboot. In the Task Manager, processes will add up to 1.3GB RAM used, but it will still show 65% used. This is not just a problem with the Task Manager; I can feel a distinct reduction in performance.