Can't power on with CF card

Buy or borrow a new Cf card. These cards, even when all the pins etc. are fine, often fail internally. They are not, as many people believe, a totally foolproof way to store data. If you get a similar problem with a different NEW card then you have to get the camera repaired professionally. Also to try would be reading your suspect card in a card reader on a pc or in another similar camera to see if you have similar problems - confirming if the card is the problem. However if the card seems to work fine in other appliances, it is probably the camera that is the problem, although Cf cards can be temperamental like that especially when they get a little old.