What works for me I think is to go to Settings->Connections->Advanced->Select Networks and set both of them to My ISP. Then I didn't need to mess with any VPN stuff as I recall.
Edit: In retrospect, it's possible my wireless sync was via Bluetooth, I don't recall, but I do remember having issues with VPN stuff and switching both networks to My ISP solved that. Updated my Active Sync a while ago to install Skype so wifi sync's not an option for me, so I can't test it. I did however find the following page with a wifi guide:
http://wifi.aximsite.com/wifi_net.html