The product distribution file could not be verified. It may be damaged or was not signed.

I have the same problem on my iMac and MacBook Pro. I called Apple tech support, talked to a level 1 and level 2 support specialist, who said it was not a problem with my computers, but with the Apple Store. They suggested I contact the Apple Store which I did, and they had no idea what the problem is either, saying my account is fine. It is clear that the Apple support people are as lost as we are, and have no idea what the real issue is. Before this, I never had a problem buying apps on the Apple Store. Very frustrating!

I found this:

"So for those who are looking for an answer to this problem, bring up the good old command line and cd to '/var/folders/' from there your experience may vary! In the sub directories in that folder, you will need to find one that multiple levels down will have 'com.apple.appstore' as a directory. Once you have found it, delete it i.e. 'rm -rf comp.apple.appstore'. That fixed it for me I was able to update my apps again!"

I have this problem too and it looks like an old problem??

The reason I own a Mac is so I DONT have to go to the command line and mess around with the guts of my computer. If I liked doing that kind of thing I'd buy a PC. When is this really going to get fixed? I requested help last night and they sent me a bunch of Dos prompt garbage which I wont touch.

It either works or it doesn't; there is no in-between. Does anybody know when the fix is coming out? Apple needs to post an annoucement about this ASAP.

the problem persist. Sorry

I am having the same issue. I have spoken to Apple twice. The first time was last night and they told me to wait until this morning. I did and still had the same issue. I called again and then was told that I should wait till tonight and hook into an ethernet connection to get onto the web, as this might be a server issue and it would work better over a hard line, instead of wi-fi. I was also told to try late at night when the server won't be as overtaxed. I have gone into the root directory and deleted the 'com.apple.appstore' as it says above and I still get the same notice:

The product distribution file could not be verified. It may be damaged or was not signed.

Anyone have any other suggestions as eventhough it's not a neccessity that I update to Mountain Lion right now, today. I'd like to just to be able to do so.

Thanks

I am also unable to download Mountain Lion, or even a couple of free ones. I then clicked Aperture to see what happened, and it purchased it (figures, it is a $80 program) and downloaded it without issue. It seems to be an apple store issue not something wrong with our Macs. I am still at a loss as to what to do as is Apple tech support.

Did you get this solved?

I had attempted a number of times to remove the suggested files. Once gone, the App store still did not work, had the same error.

At one point I saw the "flyingIcon" and "preflight.pfpkg" files were in an older version of the folder so I copied the older files to the newest folder and it worked.

When I look into that folder now it's all changed, but still working. Not sure if that helps.

for me the problem was Virus Barrier X6. Turn it off in preferences; close App store; open finder and press cmd-shift-g; type in /var/folders; look for the 2nd level folder TZ then the C folder. Trash the C folder. Open App store and download worked for me.

It runs out my Virus Barrier was stopping me from downloading the progra

Once I turned it off. No issues anymore.

for me it was both steps.. just turning off the Virus Barrier wasn't enough.. I had to delete the C folder that has the App store files... it is rebuilt when you reopen the App store....

When I did my wife's MacBook Pro I started it and turned off Virus Barrier before I opened App Store and it worked without having to trash the folder.

Many thanks for your input this has solved the problem for me.

great having so many devoted Apple users.

I've chosen not to upgrade but thanks for all the help. I have no interest in doing any of that stuff. How do I stop getting these e-mails?

Grey Day, I'm struggling with finding the "second level folder TZ." Any tips?

Thanks

Canyonlight.. the folder names might be different depending on the computer I think... the files you want will have App store in the names... for me folder "C" has all the App store files. Another way to find these is to open the Console in Utilities and then open App store and get the error message. The log will show the error file and the path which will be in /var/folders and look like "com.apple.appstore.....". Just make sure you close the App store before you trash that folder otherwise it will reappear.... with same problem. Hope this helps-- it took me several hours to figure out -- something about Virus Barrier causes this and won't let the App store files initiate correctly.....

Thanks. Was able to determine which folder from the Console as you suggested. But sending this folder to the Trash and turning off Virus Barrier still didn't work. Still getting an "undetermined error" from the App Store.