I put the whole thing down to gremlins, myself.
Hah, you beat me to it.
What happened to this site that took it offline for most of today?
Michael explained it thus:
"What should have been a relatively quick server transfer for an upgrade and ongoing services was held up due to (i) the sudden discovery of database corruption; and (ii) a seriously lackluster performance by our hosting company.
I've migrated websites countless times. This time I noticed that the usual process failed. Standard backup of the site failed, automatically and manually, and even our most recent backups were affected. Oddly, no error messages appeared to have been generated during those processes.
When you've got the potential for hardware failure and data errors that can exist even in your backups or mirrors, it's a serious issue. The site database was shut down to limit any further corruption. With some assistance from our host, we should have been able to be up and running without too much interruption. Unfortunately, I discovered serious internal limitations with our hosting company. Ironic is that it explains a suggestion I noted to them about their support system just last week, which I mentioned was not what I perceived to be industry standards. But hey, I wouldn't really need support that would be impacted, right?
With the help of senior level support which I was finally able to procure, we were able to recover all essential data. The overall backup system works as well, which I verified before putting the site back online. The entire migration still isn't complete (as they still haven't provided us with what was supposed to have been transferred) but we can finish the rest later."