Ah, it disables Windows Aero? Could it be that Windows is running it in compatibility mode for some reason? Try rightclicking python.exe (or ppython.exe - whichever one you launch) in the “python” subfolder of the Panda3D installation folder, and going to Compatibility, to make sure all compatibility settings are off.
Furthermore, try adding “notify-level-wgldisplay debug” to Config.prc. This will tell us about the pixel format that it’s selecting (including whether it grabbed an sRGB pixel format for some reason).