you're experiencing a memory leak. this is either because of large number of references aren't being cleaned up, or more likely you have a bunch of event listeners that aren't being removed.

the long answer would be to go through each loaded swiff and make sure all references and listeners are removed when it's unloaded.

if you don't mind targetting Player 10 only, there's a method called unloadAndStop that'll do all this for you.

PHP Code:
swfLoader.unloadAndStop();