There was an old hoax email that went round to the effect of:-
Your machine has been infected with the AOL virus, search your machine for anything with AOL in the title and delete it etc etc...
Although I wouldn't normally condone this type of mail in that instance it was maybe a good idea!!!
Have you tried using the
Tiscali web mail service, never used it myself but usually it gets round this problem.
As much as it pains me to admit it AOL may not be at fault here, as a lot of ISP's block you sending mail through other ISP's internet access, this prevents spammers routing mail through their servers. Weird that you can sometimes send mail however.