Have you actually changed the drive mode to "One Shot" to see if it made any difference in the shutter response time?
In addition to clearing the camera settings you might also want to clear the Custom Function settings (pg 152 in your manual). These two steps should return the camera to it's original baseline settings as when it was new.
Have you formatted the CF card in the camera? If not, be sure to download any images that you wish to save to your computer first before formatting the card. Formatting will erase all image data from the card!
You might also consider replacing the battery for the date and time backup memory. Be sure to reset the current clock and calendar info as well. The camera may need this info for certain functions.
You're lucky if you have a local camera store that you can consult. They'll likely have some used CF cards laying around that they'll let you format and test in your camera. Also it seems that the pawn shops may have a few odd memory cards stashed away under the counter sometimes. If you decide to get a new CF card, I'd try to get nothing larger than maybe an 8gb or 16gb card. The 10D may have problems dealing with the newer, larger capacity cards.
