Okay, maybe I misunderstood.

You entered a range of addresses into the SonicWall to be the ones handed out to VPN clients, right? And the VPN clients are successfully getting those IP addresses, right?

Does the SonicWall have an IP address in that range? If you can't see it configured anywhere, maybe you could ping all the addresses in that subnet and see if any other than the one configured on the client itself responds. If so, that's probably the SonicWall.

Hmm. Maybe I should take another tack and get you to post information extracted from the systems and find out whats going on. First let's get info from the VPN client.

Get a VPN client going and then post the output from "route print" and "ipconfig /all". Also try to ping one of your internal IP addresses and then do a "tracert" to that same address. Post all of that info and let's see where that leads us.