VPN across wireless connection

I am setting remote access for 6 new laptop users in the org. Several questions:
1: When connected with cable, the VPN connects with the network – Win2k3 server through SonicWall firewall using SonicWall VPN client. But attempting a 802.11g connection, it fails. Is this an issue inherent in attempting VPN with wireless?
2: When connected via VPN, I am unable to connect to shares on the older, Win2k server. Any suggestions?