We have received reports from a very small percentage of users that are having issues downloading and installing Mountain Lion. You may receive an error such as:
"The product distribution file could not be verified. It may be damaged or was not signed"
We have investigated the matter further, and we do not believe that VirusBarrier is the underlying root cause of this behavior. However, VirusBarrier is highly customizable and it is possible to intentionally configure the application to block communications that may contribute to the error above. If you receive the error message above, we first recommend that you temporarily disable VirusBarrier X6 to further isolate the issue. You can do this at anytime by following the instructions listed here.
If you have disabled VirusBarrier X6 and continue to see the same error message, please follow the instructions below which have been recommended by Apple Support for this issue:
1) Make sure that all available software updates are installed from the Apple menu > Software Update
2) Repair your hard disk's permissions in-case there are errors. To do this, click on the Spotlight search icon (in the upper-right corner of your screen) and type "Disk Utility" (don't include the quotation marks for this or any of the other text that these steps ask you to type), open the Disk Utility application, select your hard disk, and then click "Repair Disk Permissions" and wait for the permissions repair to complete. When the permissions repair is finished if any errors were shown please copy and paste them into your reply.
3) Temporarily disable any third-party antivirus, firewall, or security software that might be interfering with the connection or with saving files to your computer. Leave it disabled for the remainder of these steps. (The steps for VirusBarrier X6 can be found here)
4) Restart your computer. Make sure that any third-party antivirus, firewall, or security software disabled in step 3 remain disabled.
5) Re-try your purchase of Mountain Lion from the App Store.
6) If the error persists next try deleting the incomplete app data from your computer. Before you do this you must first totally quit the Mac App Store application (by clicking on the App Store menu > Quit App Store.) Next open the Finder, click on the Go menu > "Go to Folder…", type "/var/folders" into the "Go to the folder:" field and then click the Go button. When the "folders" folder opens in the Finder you should then paste "preflight.pfpkg" into the spotlight search field of that Finder window to search this folder for it.
If the "preflight.pfpkg" file is not found make sure that the correct folder is being searched and that system files are being included in the search. To do this:
- From the Finder window make sure that "folders" (and not "This Mac") is selected next to "Search:". - Click the "+" button to the right of "Search:" (next to the Save button) - From the "Kind" field (below "Search:") choose "Other…" - In the "Select a search attribute" window that opens type "system files" (without the quotes) into the spotlight search field - Make sure that the checkbox in the "In Menu" column is checked for "System Files" and then click OK - Choose "System Files" (which should now definitely be listed) from the "Kind" field and set it to "are included" - Repeat a search for "preflight.pfpkg", this time including System Files
Once the "preflight.pfpkg" file is found please drag it to the Trash.
7) Re-open the App Store application on your Mac and re-attempt the purchase Mountain Lion.
If you continue to have issues after performing the steps above and you have properly disabled/uninstalled VirusBarrier X6, we recommend contacting Apple directly for further assistance: