I'm using VS2010 ultimate and it was running fine untill i installed MVC3 and 4.5 preview. (With which you can ruin your whole dev environment).
After uninstalling and repair installing vs2010 I run into the problem that I cannot switch into designmode when working at a webpage or usercontrol in asp.net.
When I switch to designmode VS hangs up and only can be stopped with 3 Fingers. When I swith to mixed mode it starts to produce lots of stylsheets and adds them to my project.
In a new empty project createtes 63 stylesheet files and then hangs up in both cases.
Anyone out there who had same problems???