Do you ever find you can't open more windows within Windows.  Nice oxymoron. 

I find now and then when I have lots of windows open or ones that consume lots of memory, windows won't open any more windows until I close a few. 

I found adjusting the SharedSection data in the Windows value at the following location in the registry HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\SubSystems

I increased SharedSection=1024,3072,512  to SharedSection=1024,4096,512 which represents the Desktop Heap size which is used to store user objects like hooks, menus, strings and windows.  I've even adjusted the second number as high as 8000 with no ill effects.

This is a great article referencing that registry value:

http://blogs.technet.com/askperf/archive/2007/07/24/sessions-desktops-and-windows-stations.aspx

as well as...

http://support.microsoft.com/kb/126962