I don't know of anything that shuts the Orbit tool off. Maybe the shortcut key got reassigned or unassigned? Have you tried the shortcut button at the bottom of the 3D plane?
I don't know about why it won't render. Could be a hardware/driver problem and might be related to why it won't orbit either.
When you say it won't orbit, do you also mean that you can't move around at all in 3D, like using the walk tool?
It's possible you have something wrong with your computer as well. You didn't specify what you're running but if AC is running slow than maybe you have too weak of a computer, or you might have too many processes, or you might have virus/trojan/malware problems, or it might be hardware failing, or it might be AC has been corrupted.
Maybe a simple reinstall would be the fastest thing to try. The first time I had a problem I went to tech support and the issue was finally solved a few days later. Sometime after that I had another problem and instead I reinstalled and was up and running again in an hour. If you think AC is broken, then maybe this is a good, and quick, way of fixing it. But if you have other problems that are causing AC to function poorly then of course this won't help those problems.
