Latitude E6500 WWAN - WLAN problem

I have a client with a Lattitude E6500 running XP Pro SP3 w/2gb of ram. It has a Dell WLAN 1397 card as well as a Dell Wireless 5530 WWAN card. The client has a unique situation in his setup. He is a large animal Vet and has a totally mobile practice. He uses the WWAN card for internet access. At his office he needs to use the WLAN to access other laptops for data exchange as well as for access to the network printer. There is NO internet capability at his office location other than the WWAN cards. The problem is that when the WLAN is enabled it overtakes the WWAN as the internet source and no internet is available.

I have this same setup on a Latitude D830 and it works perfectly. I always have internet access on the WWAN and am able to use network resources on the WLAN.

I need to duplicate this on the E6500. I have spent many hours on the phone with Dell Pro Support to no avail. Per support I have removed the Dell Control Point connection manager and have gone to using Windows for WiFi access and a seperate ATT card utility for the WWAN card. I have been able replicate the D830 on a couple of occasions but have not been able to get the E6500 to hold the settings after a reboot. This tells me that it is possible on the E6500, but I need to be able to make this perminent.

I would appreciate any help or comments anyone may have on this problem. I realize that this is an uncommon setup, but it is what I have to work with.