I just thought I'd give a heads up on this experience, I don't have the time to reproduce this issue as it required me to pave my machine to fix.
I've been using VS 2010 Ultimate with ReSharper 5 (Release) with a couple silverlight and wpf projects one mid-size and one small. Performance is perfectly fine.
I installed the latest version of Code Contracts Premium from here: http://msdn.microsoft.com/en-us/devlabs/dd491992.aspx
After installing this VS would basically lock up, especially after opening XAML files. The problem would occur a min or so after opening the solution. Until that minute was up I was able to navigate any files in the solution just fine.
My extreme quad core would then be pegged at 30 percent, all cores interestingly enough, and VS would only process commands every 30 seconds to a couple minutes.
I tried disabling solution wide analysis and color highlighting to correct the issue, no improvement at all. Suspending ReSharper solved the problem.
I also tried uninstalling Code Contracts, uninstalling and reinstalling ReSharper, and installing the latest EAP of ReSharper. None of these helped.
The only way I could keep ReSharper was to pave my machine and start over. Everything is back to normal after getting my environment back to its state before installing Code Contracts.
Perhaps the Code Contracts installer corrupts the VS install, adds some bad mojo to VS, or it was just one of those things.