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Causes windows 7 desktop window manager (wdm.exe) to use large amounts of memory

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Whenever I have Firefox4 open, it causes dwm.exe (Windows desktop manager) to use large amounts of RAM - It starts at about 100MB, quickly increasing to about 1GB over 20 seconds, then dropping back down to 100MB and so on. It does this continuously while Firefox4 is open, with the occasional "Your computer is running slow" message being shown by Windows.

Update: Only occurs when browser isn't on the primary display on a multi-monitor setup.

Whenever I have Firefox4 open, it causes dwm.exe (Windows desktop manager) to use large amounts of RAM - It starts at about 100MB, quickly increasing to about 1GB over 20 seconds, then dropping back down to 100MB and so on. It does this continuously while Firefox4 is open, with the occasional "Your computer is running slow" message being shown by Windows. Update: Only occurs when browser isn't on the primary display on a multi-monitor setup.

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I had the exact same problem. DWM would use massive amount of memory when Firefox 4 was open on my secondary display, especially when scrolling with the mouse wheel. It would use so much that Windows 7 (8GB RAM) would turn off Aero. Going into Options>Advanced>General and unchecking "use hardware acceleration" fixed the issue. Of course now I can't take advantage of any hardware acceleration.