Sent some of my teen sims to college, The first day or so all was fine, but now some of their dorm mates look like ghost, but they are not dead. They are see through, but they act normal not like ghosts.

It's because sometimes when they leave their dorm room they don't materialize all the way, for whatever reason. They will usually fix themselves the next time they enter and then exit their dorm room. Or, if it really bothers you I believe you can use the Batbox to fix them, under "Fix..." and then "Invisible Sims."

Oh ok thank you so much was afraid I had messed up my game some how.

Dormies have a habit of becoming invisible, too much bubbles if you ask me. But no, nothing to worry about unless it's happening wide scale, then maybe it could be something.

Sometimes switching into buy mode and then back to live mode fixes this as well. Also the bug where you can see a dormie inside their room but not the furniture. You should always fix the latter, because if you leave it their motives can get stuck going down but they can't move or leave the room to fulfil them.

That happened to me too. Being a new player, I thought the guy had died. He was a Sim my girl was trying to befriend, and when she approached him as a "ghost" he argued with her. I thought, Oh, he doesn't like her since he died. So then I worried that she had accidentally killed him. But then he was back to normal again. Thanks for the explanation of what was really going on.