Windows file sharing across subnets

I have a SonicWall TZ170 wireless router that will not allow the LAN and WLAN to have the same subnet IP address. I have a WinXP Pro desktop on the LAN at 192.168.70.100 and a PowerBook on the WLAN at 192.168.71.100. The router firewall is set up to allow all traffic (any IP address) between the two subnets. However, no matter what i do, I cannot get the PowerBook to connect to the PC. (I've also tried SMB://192.168.70.100/share, where "share" is the name of the shared folder on the PC.) I know the file sharing settings are correct, since I can mount the PC share when the PowerBook is connected to the LAN.

I've since read that SMB does not work over different subnets. Is this correct? If so, is there any other way to share files on the PC with the PowerBook?

PowerBook G4 15 Mac OS X (10.4.8)