[electrongun]

There's a thread somewhere, with an easy non-permanent solution and a more complicated permanent solution.
I only remember the easy way which consists of going to settings/SD & phone storage/unmount SD card, then you should be able to download your updates after which you can re-mount your SD card.
I think the more permanent way was to move all your apps on the SD cards back to the phone's memory and then back onto the card. Not sure though...