Most have to do with being patient. We require students register their computers and when you have almost 900 people doing this over the course of a day, the system goes a little slowly. Some students are fine, but need to wait a bit, and this isn't always obvious. But people understand once you explain.
Also had one computer with a broken network card, so there's not much we can do. Luckly, it was near a wireless access point, so that can be used until the card is fixed.