My iPhone has become worthless

As of around 1pm yesterday, the following is the state of my iPhone: all contacts gone, calendar app won't open at all, can't send/receive email.

Happened seemingly spontaneously.

I suspect this has something to do with MobileMe, Exchange, or a recently added gmail account. Thing is, I can't edit any of my mail or sync settings- when I try, Settings either freezes or just ignores my changes.

I did a full software restore last night, to no avail.

This really sucks. Anyone have any ideas?