Here a link that has suggestions from Microsoft:
http://social.msdn.microsoft.com/Forums/en-IE/ieextensiondevelopment/thread/b460a583-997c-42a7-a016-3630ada642f1
They recommend the following
"Local Administrators can control DEP/NX by running Internet Explorer as an Administrator and unchecking the Tools > Internet Options > Advanced > “Enable memory protection to help mitigate online attacks” option."
If the above does not help then you can check the following as recommended by Microsoft:
http://support.microsoft.com/mats/slow_windows_performance/en-us
For Windows 7 alsothis one:
http://windows.microsoft.com/en-US/windows7/Diagnosing-memory-problems-on-your-computer
Then try to perform clean boot and update your windows and java with latest patches.
