I just installed Orcas and was getting this error when running a performance test:
Event Type: Error
Event Source: ASP.NET 2.0.50727.0
Event Category: None
Event ID: 1062
Time: 11:11:12 AM
It is not possible to run two different versions of ASP.NET in the same IIS process. Please use the IIS Administration Tool to reconfigure your server to run the application in a separate process.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Running aspnet_regiis -i fixed the issue. You should be all set to run Orcas on new sites you create, but you’ll need to manually set 3.5 for that site.