Same issue here as well. Even tried reinstalling from the recovery, it downloaded again and installed 10.8.1, no update found in the app store and the combo gives the same message you are getting. Can't seem to find an anser any where on it.
Apple removed the update from 10.8.1 to 10.8.2 today!
The combo updates are for the earlyer macs, but the 2012er versions have a special 10.8.2 build,
i tried to download the special combo update for my mac mini 2012 but the download link
from apple is removed too!
i think we should wait