Cannot Install or Update Apps in App Store - Error 13

I can currently no longer update or purchase software in the Mac App Store.

I have cleared Safari's cookie cache, cleared ~\Library\Caches\com.apple.appstore logged in and out again, but none of these help.

The error message is:

We could not complete your request. There was an error in the App Store. Please try again later. (13).

Anyone else experienced this? Any fixes?

In the console I am seeing:

17/08/2011 15:30:15.384 com.apple.SecurityServer: Failed to authorize 
right 'system.install.software' by client 
'/System/Library/PrivateFrameworks/PackageKit.framework/Versions/A/Resources/installd'     

[6043] for authorization created by '/Applications/App Store.app' [9337]

Update: I logged in as admin and the App Store works fine. So some sort of Prefs file is hosed in my main user. Does anyone know which one it would be?

I seem to have fixed the problem.

I used opensnoop to follow all file accesses while the app store was running. I spotted that ~/Library/Cookies/com.apple.appstore.plist was being accessed - this file had not been deleted by Safari when I cleared all cookies! The file had incorrect permissions - I deleted it. Now the App Store seems to be working again.

Opensnoop is a great tool!

This post seems relevant: http://www.ryanragle.com/index.php?/site/comments/where-does-the-mac-app-store-download-temp-files-to

What worked for me in the end was this:

1. Per post above, enable debug menu via

   defaults write com.apple.appstore ShowDebugMenu -bool true

2. Sign out

3. Clear cookies AND reset the app, using debug menu
4. Select Menu->Store->Check for unfinished downloads
5. Wait for the downloads to finish and then
6. restart the app store app.