Hi class,
It's because AOL use blacklists, into which go any mail server addresses used by spammers. Unfortunately (and many other "free mail" accounts) are often abused by spammers and many of their servers (though not all of them) are now blacklisted. Some have got around this by using a new account (I guess it works because new accounts go through new, and previously unabused, servers) although this probably won't work forever.. it's only a matter of time. You might want to try setting up another disposable address, such as with and send with that as the from and reply address - you should be able to configure your software to do this for you. It will still provide at least some level of anonimity.
You can apply to AOL to have your address removed from the AOL blacklist, but I've not heard of anyone succeeding.
I hope this clarifies the situation a bit.
Mandy