One more Apple fuck-up to add to the list. The Mac App Store doesn’t work correctly if you have Spotlight disabled. Why the fuck do I need to run a disk indexing application just to buy/update other applications? This doesn’t bode well for their Lion delivery method.
For reference, if Mac App Store gives you an error saying “You have updates available for other accounts” and you get an entry in the Console Messages saying “Multibyte IDs are unsupported”, you’ll need to re-enable Spotlight, or remove your HD from the Privacy settings in Spotlight.