Asp.Net Impersonation over a VPN

Question

I'm doing a spot of development from home over a VPN. The project is an Asp.Net 2.0 (Using 3.5 SP1) app that uses impersonation. The account that is impersonated is on the domain at work but when ever I attempt to run the app I get the following error:

'Logon failure: unknown user name or bad password.'

The impersonation is required for the app to access the SQL Database located at work. The connection string fully specifies the Server + domain.

Any ideas what it could be? or resources I could look at?

Cheers Tony