As of this morning (almost 4 AM!) I got the site back up and running, having (almost) completed the server relocation. Sorry about the two week hiatus; it was almost as stressful as moving house due to the size and complexity of the site. Unfortunately, all of this coincided with me going on holiday and my American host's subscription expiring. After all the aggro and lousy service of the last month, I was damned if I was going to resubscribe for another two years of grief. And they were damned if they were going to give me my three months compensatory free service unless I did. Suffice to say, we're now hosted on shiny new servers in the UK with a support team eager to troubleshoot within minutes any time of the day or night. Hopefully, you've already noticed an increase in page loading speed.
There are still quite a few issues to work on (Market, Auction & Site Search down for now), which I'll be tackling about a week from now.
Meantime, I've updated the Forum software, deleted a load of spam bot accounts and made some changes to prevent bots from registering.