Wasn't the issue with lunarpages that they would put you on one of their short bus servers if you used too many resources?
That did happen to me once a couple years ago. And it turned out it was some oddball search engine spiders pinging my PHP files like crazy - driving up resource usage. So I blocked some IP's and updated my robots.txt file and all was well again. It did take me some time to get through to a tech that could help me resolve the issue other than just blankly say "reduce your resources usage."