You mentioned that you pinged a site... however saying that one "hop" succeeds seems to imply you ran a traceroute instead. Which are you using? Knowing what hop your packets are getting dropped on should show us where the problem lies (or at least point us in the right direction). If you are not using traceroute, give it a try: tracert aol.com
The WRT54G is notorious for getting overwhelmed with open connections, especially if you torrent. However, if you have already tried power cycling both it and the modem to no avail, the the problem may be with you ISP. Have you tried contacting them about this issue? You might want to also ask around to see if any of your neighbors are experiencing a similar issue.
The issue could also be with the PC itself. Do you have any other devices you can plug into to verify it's not the PC?