SQL Datasource access via VPN

Hi, I am hoping someone here might know enough about SQL permissions to help me with this.

I have a RDM datasource configured on a SQL2005 Express instance on SBS 2008.
I can access this database fine from the workstations within my network.

What I am wanting to be able to do is access this database from my laptop which i VPN to my network with, but I keep getting SQL connectivity errors.

My laptop connects via the VPN fine, I get full access to every other resource on my network, except for this database :(

Any one have any pointers?