Unfortunately, there's so much variation in server configurations it's pretty much impossible to get everything to work everywhere. I've worked several forums (at least two on GoDaddy) that could not be upgraded in place. Had to export database, upgrade it on my server, then move it back. You also have the problem of very old forums running early 1.1.x that have never upgraded, and are in a panic because it stops working. That's why there's a support forum, but sometimes it's impossible to talk them through it, and you have to get into their host and do it for them.