Oly E-500 Card error
want to buy a new battery, but have you checked the battery contacts? dirty or bent contacts could have the same effect as a weak battery.
Agree that if there's a firmware upgrade, do it, but only after you are sure the battery is fine!
Other options seem to have been covered- if it's not the card or the battery, then it must be the camera... and whatever a CF card costs, it will be cheaper than sending the camera in for service.
"I am a creature of contrast,
of light and shadow.
I live where the two play together,
I thrive on the conflict"