[Verbose]

First, don't use Godaddy for anything.. they lose domains and um.. apparently charge you by the hour for server maintenance. Especially if you are serious about your site/forums - and it sounds like you are if you have over 50K members. Trust me, get a REAL webhost (and while your at it .. move your domains to a different registrar like Namecheap, that isn't run by someone like this toolbox).

Last week, I had my host (Choopa.com) upgrade mysql, php, apache, etc etc. - it took them about 3 hours b/c they actually setup apache on a new box and copied all my sites and databases over. When they were done, vBulletin ran fine with no errors of any sort.

I run a dedicated box, so i don't share resources with other sites - whenever I need to upgrade or mess with the server, tech support is on it. I do NOT recommend you try to upgrade yourself, unless you know what you're doing and have backed up your database, etc. A good webhost will go a long way to keeping your sanity and peace of mind