Difficult ICS Between Win XP SP2 and 10.4.2


At school the only way to gain internet access is through a windows PC with an 802.11a card (yea we all know it blows) I have my mac here and I am trying to setup an adhoc network and connect through ICS that way. In my computer I have an 802.11a network card which gets the internet access and a linksys 802.11b/g card which i am creating the adhoc network on and connecting through with the powerbook. I can connect to the adhoc network perfectly fine and ping the other host on the network. However I shared my internet connection on the windows machine (802.11a) and shared it with the b/g card. I can't access the internet on my powerbook. I also tried bridging the connections (the a card and the b/g card) but when i do that it disconnects me from the internet on the windows machine.

Has anyone dealt with anything like this before or does anyone have a good suggestion?