VS2010 debugging SL 4, can't load source code from source server

I am attaching to an IE instance which is running my deployed SL 4 app. All symbols load ok but when the debugger hits a breakpoint instead of loading the source code from TFS it says:

SRCSRV: Unable to determine source server information for module 'MyDll' because it is not fully trusted.

The website is a local LAN website like https://someapp.domain.local/

I added the website to my trusted sites list but no luck. What is the problem?

Cheers

Update: reported the problem on microsoft connect here

Got the solution for this:

Create this key in the registry:

RequireFullTrustForSourceServer = 0 (REG_DWORD)

at:

HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\9.0\AD7Metrics\Engine{00000000-0000-0000-0000-000000000000}

Disabling full trust for source server is a security threat. For visual studio 2010 adjust the registry path accordingly.