I wonder if this is related to the Quicktime RAM leak I keep hearing about?
Apparently the Quicktime X library isn't very efficient and leaks a bit of data which makes your RAM fill up; after a while it can make your computer become slower. The only way to stop it is to flush your RAM out by restarting the application.
Of course the bigger your RAM the less its effected.
I am not a programmer though so someone is bound to know a lot more about this than me. It might not even effect resolume - I am just wondering/pondering.