Currently Being ModeratedAug 26, 2012 8:41 PM (in response to d2568)
Here's the article: http://support.apple.com/kb/HT4649
(macjack, I found I don't have permission when I tried to read the appleseed article.)
Bottom line: as macjack suggests, it looks like you're trying to install on a RAID or non-standardly partitioned disk. The article suggests a lot of Mountain Lion would work this way, but not everything.