Some websites timing out from time to time

So, I have had the weirdest problem lately. Periodically, various websites (Google and Livejournal immediately come to mind) just won’t load. The connection just stubbornly times out, as if I were having some problem connecting to the internet.

The thing is, all my instant messengers (AIM via Trillian, and Yahoo Messenger) and IRC work just fine. In fact, many websites still work fine. At the very same time that I am unable to access Google or Livejournal, I can go to many other websites, ie: I am posting here on the Straight Dope Message Board with no problems at all, while LJ and Google are both timing out. This has happened to me in Texas with Cox Cable, and here in Arizona with Qwest DSL. My room mates’ computers in Texas, and the family computer here in Arizona do not suffer from a similar problem.

So, any ideas on what could be up here? I’ve run AVG Anti-virus, online virus scanners such as Pandascan and Trendmicro Housecall (IIRC), and Ad-Aware SE, and the problem persists.