I have no idea. I've never used AOL myself. (I don't even know what it looks like)
Go to Tools, Options and then Bug Report and click for an example. Scroll down to where it says: "Recieved incoming this session". If it says false, then a firewall is indeed blocking your access.
Do you have a router (very often these have their own firewalls)?

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iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

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