"Another cause may be the Autofocus motor?"
If it was the Autofocus motor, that is inside the EF lens, so you could remove the lens from the body and test it again very quickly.
I've shot with Canon EF lenses for 14 years, and I have never had a lens start making noises like that. If the autofocus fails in a lens, it just quits dead, or else it keeps giving you bad focus results.
I _think_ that there are capacitors inside the body that charge up to energize the electromagnetic shutter. So, if there was a capacitor failure and the body could not ready the shutter, I could understand noises.
Don't take this the wrong way, but...
In a camera like a 30D, there are only so many thousands of shutter cycles designed into the body. That body is several years old, and we don't know if it has seen light use or heavy use. It is quite possible that the shutter system has gotten old and has failed. If you think this is so, you can send it to Canon in Irvine, and they will assess it and tell you the repair price, and you can decide if it is worth it or not.
In the professional camera bodies, the shutter systems are designed for two or three times as many shutter cycles, since professionals shoot a lot. But, those are $$$.