Another strange bug

So I sent one of my sims to university, and everything seemed normal. I shut down last night after a couple of game days at uni, then decided to play a bit this morning before work. I found that he was unable to interact with a sim there. I looked for that sim in his Relationships panel, and found that not only she wasn't there, there were only four sims there, all at uni - his family and friends from back home didn't show. Then I clicked on his family tree to see if they were there, and there was nothing but him - and he was greyed out as if he were dead.

Fortunately I'd saved just before sending him to uni, so no great loss - but has anyone else encountered this one?