When I use shutter speeds in excess of 1/600th of a second, I get a thin light strip at the very top of the frame. I use Sandisk Extreme IV, 4.0 GB so I don't think the card is at fault. The same happens with other cards, the Extreme 3, e.g. Any thoughts?
Regards,
Gert

Can you post an example photo?

Sounds just like my 1DSmkII shutter fault, same symptom.
Shutter was replaced under warranty.

are you using a flash? if so, you're exceeding the sync speed.

It's irrespective of using flash or not. I think I'll just take it to the repair shop and ask them to take a look at it.
Gert