Windows 7 Desktop Windows Manager memory leak?

I couldn't find Windows-7 groups, so I'm posting here. Please redirect if
required.

On PCs where the user remains logged in, but is not using the mouse or
keyboard, the memory used by the DWM continues to increase until some mouse
or keyboard activity takes place. On my PC Hydra, for example, DWM.exe uses
up to 600MB, and appears to cause other applications to give up their own
working set. PC Stamsund shows similar problems, but I tend to use that
every couple of days.

http://www.satsignal.eu/2009-Dec-07-dwm-leak-hydra.png
http://www.satsignal.eu/2009-Dec-07-...k-stamsund.png

Has anyone else seen this sort of behaviour?

Thanks,
David