AOL 6 on Win98 PC to over NT Network?

I administer an NT network – recently we reconfigured the Exchange Server. Prior to the reconfig, some users had AOL 6.0 installed on their workstations and they were able to use (not thru a browser but actually using AOL software). Following the reconfig, the systems will not log on to AOL claiming a TCP/IP error/conflict. I spoke with AOL support (you guessed it – an Oxymoron), and checked all the Proxy Server settings, but I cannot get it to run. How did it work previously – the person who ran the network before had everything jerry-rigged and we are trying to move towards established standards and protocols. Any suggestions? Please HELP!!