Have you contacted Canon support?  Since you did more than what the
FAQ for that error.

Err 05
   
Something obstructed the built-in flash's automatic pop-up operation.
Turn the power switch to <OFF> once, and then switch it to <ON> again.

http://alpha02u.c-wss.com/inc/ApplServlet?SV=WWUCA900

*********************************************************

"I have been a witness, and these pictures are
my testimony. The events I have recorded should
not be forgotten and must not be repeated."

                             -James Nachtwey-
                        http://www.jamesnachtwey.com/

Had the same problem yesterday and all I did was give a gentle pull on the
flash while pushing the flash release button in Program Mode.  The flash
popped up and hasn't stuck down since.  I'd guess that the release is not
working properly so I'll probably send it in for repair but that will have
to wait until the new year.

Peter, I just sent my 20d into the service factory center in Irvine
California for the exact same problem.  What actually happened was, I
was  wearing a baseball cap, I usually don't use the Auto settings, but
for some reason I had it set to auto, the flash popped up a couple  of
time and hit the brim of my hat.  Then I got the same error.

I sent my 20d in on Monday Dec. 5th and got it back repaired on Tuesday,
Dec. 13th,

All I had to pay was shipping and insurance.

It was all under warranty.  I believe there are lots and lots of these
issues out there with this camera. They should have made it without a
flash, that little flash is just about worthless.

mikel

 Does it click at all?  I had that error once when the popup flash on my
RebXT had taken too much of a beating.  I wiggled the flash as it clicked
and tried to come up, that unstuck it, and it's worked fine ever since.

steve