Same Exact message. I was prompted to update BY the Apple updater.
I DO have java, and I had no problem at all with the recent update 2012-002.
Tried 3x now, same result, the same message as you get. It was "corrupted during downloading"??
('may have been'). This is the first time I've had this issue and error message. A bad "fix"??
Thanks so much for this same-day, world-class speedy response!
HOWEVER, when I have tried (4 times so far) to download, the sequence is:
Download-Install-Write-Cleanup- ERROR MESSAGE. No further option except "OK", and it closes.
Where exactly does one find a "Click on the Open Anyway" button?? Would love to, but have never seen one.
UPDATE on the Update - Solved!
Went to the Support Page (thanks Linc) and downloaded not the updater but the update.
A few more steps (like entering password and watching as the system 'optimizes' and moves files). And voila, big green check mark. Successful.
Mystery to me why the normal and always-before-successful updater updating yields that error. (Apple?) :-)