So, I was building 4 server medium-ish farm on Friday, and everything when fine until i spun up the first site collection just to test the Office Web Apps install -- and then it failed; "Trail Period has expired" - hmm.
RTM software - check
Right product key - check.
Very wierd - so, I found this post of a similar problem, and sure thing it worked. Adding more rights for the app pool account did the trick.
I want to investivate this a bit more, so I'll update, if I find a solution without giving more access rights.