EOS 10D Shutter Problem?

My camera's shutter button seems to be causing a problem. About 70% of the time I have to hold the button down very hard or for about 2 seconds before the shutter responds and the photograph is taken. I have a BG-ED3 battery grip attached to the camera and when I use the shutter button on the grip it responds intantaneously, like normal.

It seems to me that the shutter button is wearing out, do you reckon my diagnosis is correct? Any tips?

Sounds about right. If you sent in to Canon they would replace the whole top of the camera.

Edit: I just noticed you have a 10D. The above assumes they still have the part for it.

Are you sure you aren't on one shot? If you are, then it may be that the focus mirror isn't up to spec and probably causing low keeper rate as well (assuming no user error on your part, and assuming you know well enough that in low light the camera will not get focus quickly and may happen even when there is sufficient light)

EDIT: Though the one to the top is the likely problem/solution, I'm just throwing other possibilities out there for you.

If you half press the button too long there is a delay on shutter release. If not then probably a small button switch needs replacement. Not expensive and is pretty easy job.

Just the button wearing out. The one on my older 20D is a lot less responsive than my 30D.