New Visitor Here with Question

Hi All...
I am hoping someone out there has some info for me.

I'm shooting with a 10D and have had no problems with it for about 1.5-2 years now. I guess it was time for something to go wrong.

I have the ERR 99 message. I've had it before, but a quick on/off fixed it. Now, it won't go away. I've:
Taken the battery out and replaced (new and old)
Switched flash cards
put on new lens (canon Ls)
used the 550EX flash and the built in flash

nothing has worked.

Is there anything else I can do and if not where is a reliable, affordable, place in So.Cal. to take it in?

Thanks!

The Canon factory repair service is in Irvine CA.

---Bob Gross---

Have a quick look at your contacts on the lens mount and the lens to make sure that they are clean.

Did you check the back-up battery (the button cell)?

I took it into Canon and it was the shutter.
So, I'm getting everything cleaned and spiffied up and a new shutter. Costs me about 200$. Not bad I suppose.

Thank you to those who offered suggestions. I really appreciated it.