Booted with SL, used sudo mdutil -E on the Lion volume, saw a bunch of these, but reindexed in about eight minutes. I'll check later by booting into Lion. If the issue persists, then it's time to file bug reports. Upgrading to ML won't help those stuck in Lion. The problem needs addressing by Apple.
Sep 28 10:17:09 localhost mdworker[1970]: Cannot find factory 548A3091-3C5D-498A-A329-B532A6C896BB
Sep 28 10:17:39 localhost mdworker[1970]: CgBI: unknown critical chunk
Sep 28 10:17:45 localhost mdworker[1970]: Cannot find factory FC0957C6-10A1-469B-AA54-5A9FFE718A93
Sep 28 10:17:45 localhost mdworker[1970]: CgBI: unknown critical chunk
Sep 28 10:18:19 localhost mdworker[1970]: Cannot find factory 548A3091-3C5D-498A-A329-B532A6C896BB
Sep 28 10:18:19 localhost mdworker[1970]: Cannot find factory 548A3091-3C5D-498A-A329-B532A6C896BB
Sep 28 10:20:33 localhost mdworker[1950]: iCal.mdimporter: could not find component keys: /Volumes/Lion/Users/username/Library/Application Support/iCal/Sources/648D1455-E922-475C-8F0E-559FC74F0F80.calendar/corestorage. ics
Sep 28 10:20:41 localhost mdworker[1950]: failed to get locale ID from LCID 854
Sep 28 10:24:05 localhost mdworker[1950]: Error, could not create MachMessagePort for com.apple.AddressBook.abd
Sep 28 10:24:06 localhost mdworker[1950]: *** Failed to decode 7bit; data, treating as binary