Trusted Connection to SQL fails after connecting to a VPN

I was also having this same issue and found the solution here:

http://social.technet.microsoft.com/forums/en-US/itprovistanetworking/thread/275599f0-6239-46a5-8245-50a5c13a2713/

You'll need to locate your VPN connections .pbk file.

You can find it here:

C:\Users\{WindowsLogin}\AppData\Roaming\Microsoft\Network\Connections\Pbk

Or if you have it set to allow all users to use the connection, you can find it here:

C:\ProgramData\Microsoft\Network\Connections\Pbk

Edit it with a text editor and find the line that says:

UseRasCredentials=1

Disable it by setting it to 0

UseRasCredentials=0