Sounds like a memory leak! To find out, go to "About This Computer" in the Apple Menu and note the amount of System memory being used. Do this before opening VW. When VW starts to get sluggish, go back to the "About This..." from the Finder and see if it is showing a large increase.
You might also need to increase the alotted amount of Ram for VW in the "Get Info" window (I suggest at least double the "Prefered" amount.
You might also consider installing the max amount of SGRAM - Ram is pretty cheap right now.
Chris
