@Paul, I've been getting the same failure for days now. Clicking "Update All" pretty much always fails and if I update one at a time I get fail, fail fail, succeed, fail, fail, fail, fail, succeed,... And it seems to be getting worse.
Updating apps from my phone instead of thru iTunes seems to work much, much better, but I still get failures on the phone too.
I don't think it is anything on users' end. It really smells like Apple is having a capacity issue. Maybe they are fighting off some kind of attack like a Denial of Service or something and don't want to admit while their are engaged with fighting it.