Pam's probably got it right, but another solution you could try is to delete the beds and replace them. It's possible the bed ownership has gone strange on them.
If I remember right you're playing with the latest patch but not the latest expansion - when I was doing the same I had trouble with setting and unsetting bed ownership. I'd recommend not setting it at all, and using door locking if you want to keep certain sims out of certain beds. I might be recalling it wrong, but I think when my roommate joined the family and I kicked him out then invited him back in as a roommate again, he couldn't sleep in his old bed because it was assigned to the old version of him. The university features are a bit quirky without university, as you've noticed!
And if you do need or want to reset a sim, hit ctrl+shift+c, type resetsim firstname lastname, then hit enter. So it'd look like:
resetsim Darstan Cantsleep