I'm guessing it's to do with some kind of AOL traffic management.
The command prompt ping and tracert applications work by sending a special type of request to the remote server.
The "ping" in a game is usually measured by sending a packet of regular TCP/IP data to the server and waiting for a response.
The times 4pm-midnight sound suspiciously like they are managing traffic between these hours, and could well be a symptom of the 'upgrade' you just signed up to.
Not convinced it's to do with the server being in San Fran, because their busy time would be later on when everyone gets home from work, not the other way around.
Unfortunately I strongly suspect that the problem is with AOL, especially if it coincided with your 'upgrade' going through. If so, I'm afraid there's not an awful lot that you can do about it, except complain bitterly enough in order to try and get a MAC code out of them and get out of your contract.
Not much else I can suggest, I'm afraid.