I had a fun afternoon a few months back when all the imagecache images broke on a site I'd just taken live. I've just figured it out, so I'm telling you about it.
This was the situation:
- subsite.client.com was where I was developing the site, one of a family of multisites.
- subsite.com was a parked domain that went to just this site. It was this I'd just pointed to the IP of the box and that wasn't showing any images.
On the development domain, all worked fine. On the subsite domain, nothing.