It's been a long time since I shot my 20D (my daughter still has it & uses it) but I do remember having problems if the ON / OFF switch was just a bit less than in the ON position. It may look to be in the ON position but see if you can move it even more ON or switch it off & then back ON. Also I guess the date / time battery could cause problems when it goes dead but I don't know just what problems so check your manual if my first suggestion doesn't fix it.
"A skill is developed through constant practice with a passion to improve, not bought."
