Problems with netgear firewall & VPN

Was wondering if anyone had come across this before.

Background
We have a 3com VPN solution that’s been working for some time and have some Netgear equipment on remote sites to connect back to us over VPN, everything was working fine for a good year.

We then moved from NT4 domain structure to AD 2003 and this is where things started to have some problems.

We are using the Safenet client to connect and we get a nice key and when we check the VPN log the user has connected but they cant access there email or map drives, if we log back onto the lan using NT4 account everything is fine.

It was at this point I thought it was an issue with the VPN device but this week we had a 2wire ADSL router from BT set up and tested that and we logged on first time we can get email, map drives, access the intranet.

So it is looking like there is some issues with the firewall on the Netgear equipment, and looking for any advice or to be pointed in the right direction of some material that can help me.

KIT

VPN Harware
3com SuperStack 3 Firewall
Firmware version: 6.0.2.0 (yes I know there is an update but installing that is not an option at this time)

Netgear client hardware
Netgear ADSL Firewall router DG834
Firmware Version V1.04.01

Netgear FVS318 Prosafe VPN firewall
Firmware V2.3

We have some other Netgear models out there too and they have the same problems but I cant get there model numbers right now.

Hoping in advance someone has seen this and knows a solution.