[MonoDevelop] Buggy Monodevelop

[pinggi at centrum.cz]

Hi, after some time I installed Monodevelop 2.8.6.5 - stable release. Then opened my asp.net web forms project and changed fw target version to Mono / .NET 4.0, rebuilt it and run in debug mode. In a one second I got:
 
Debugger Error: The operation failed because debuggee and debugger are on incompatible platforms. (Exception from HRESULT: 0x80131C30)
 
So I searched for solution to this error on the internet. I found one comment that it is needed to change Target platform to x86, so I did, but got the same error.
I tried changing configuration from Default Runtime to Microsoft .NET. The same error. Then I changed to Mono 2.10.8. and run in debug mode.
New window called "Exception Caught" appered with content "Method not found: 'Mono.WebServer.XSPWebSource..ctor'". I clicked the "Close" button and upset I'm writing here.
 
Is this really "Stable release" ?