App Store "An Unknown Error Has Occurred", Apple Support fix was only temporary. How fix permanently?

When opening an application installed from the App Store (TextWrangler) I am prompted to sign in. After entering the correct Apple ID and password I get an error, An unknown error has occurred. This only happens with one app, other apps installed are OK.

This error also occurs when I sign in to the App Store. So its not just affecting a single application.

This also seems to be affecting my iCloud login. It prompts for a password then just seems to hang.

I spoke with Apple Support yesterday. They had me delete all Caches from /Libary/Caches, ~/Library/Caches, and a few cookies then restart my iMac. This fixed the issue yesterday. Today I start my Mac and get the same error again. I called Apple Support and got the runaround, I was told to use ExpressLane which doesn't really seem to have a solution.

How can I permanently fix this error?

Previous attempt to identify/triage the error

Searching online turns up similar suggestions to clear caches and cookies, but also some more extreme suggestions involving network settings that I am hesitant to try.

Logs after starting TextWrangler and being prompted to login:

9/19/12 10:01:30.611 AM com.apple.backupd[889]: Couldn't find en0.
9/19/12 10:01:30.638 AM com.apple.backupd[889]: Backup completed successfully.
9/19/12 10:01:58.592 AM RockMelt[306]: Cannot find function pointer CMPluginInFactory for factory 3487BB5A-3E66-11D5-A64E-003065B300BC in CFBundle/CFPlugIn 0x796aa090 </Users/jon/Library/Contextual Menu Items/Google Notifier Quick Add CM Plugin.plugin> (not loaded)
9/19/12 10:01:59.885 AM RockMelt Helper[931]: Internals of CFAllocator not known; out-of-memory failures via CFAllocator will not result in termination. http://crbug.com/45650
9/19/12 10:02:00.615 AM RockMelt Helper[931]: CGSLookupServerRootPort: Failed to look up the port for "com.apple.windowserver.active" (1100)
9/19/12 10:02:07.797 AM WindowServer[89]: CGXDisableUpdate: UI updates were forcibly disabled by application "RockMelt" for over 1.00 seconds. Server has re-enabled them.
9/19/12 10:02:11.035 AM WindowServer[89]: reenable_update_for_connection: UI updates were finally reenabled by application "RockMelt" after 4.24 seconds (server forcibly re-enabled them after 1.00 seconds)
9/19/12 10:02:34.240 AM Blink Lite[310]:REDACTED
9/19/12 10:03:07.693 AM com.apple.launchd.peruser.501[192]: ([0x0-0xae0ae].com.barebones.textwrangler[938]) Exited with code: 173
9/19/12 10:03:39.054 AM librariand[951]: MMe quota status changed: under quota
9/19/12 10:03:40.741 AM com.apple.security.pboxd[959]: Bug: 12B19: liblaunch.dylib + 23849 [224CB010-6CF8-3FC2-885C-6F80330321EB]: 0x25
9/19/12 10:04:00.293 AM Dock[205]: LaunchPad: __53-[LPAppManager(StoreSupport) _acceptStoreConnection:]_block_invoke_0 app store xpc message error: Connection invalid
9/19/12 10:06:11.123 AM TextEdit[949]: SCNetworkReachability server not available
9/19/12 10:06:11.124 AM TextEdit[949]: SCNetworkReachability server not available
9/19/12 10:06:11.130 AM TextEdit[949]: socket(PF_ROUTE) failed: Operation not permitted
9/19/12 10:06:11.000 AM kernel[0]: Sandbox: sandboxd(990) deny mach-lookup com.apple.coresymbolicationd
9/19/12 10:06:12.423 AM sandboxd[990]: ([949]) TextEdit(949) deny mach-lookup com.apple.SystemConfiguration.SCNetworkReachability
9/19/12 10:06:12.426 AM sandboxd[990]: ([949]) TextEdit(949) deny system-socket
9/19/12 10:08:22.725 AM com.apple.launchd.peruser.501[192]: ([0x0-0xbd0bd].com.barebones.textwrangler[1015]) Exited with code: 173
9/19/12 10:09:00.951 AM Dock[205]: LaunchPad: __53-[LPAppManager(StoreSupport) _acceptStoreConnection:]_block_invoke_0 app store xpc message error: Connection invalid

Solution 1:

I found a solution. Another forum post describing similar issues suggested deleting /Library/Preferences/SystemConfiguration/NetworkInterfaces.plist. I backed that file up, deleted it, and restarted. I can now log in and out of AppStore, access all of my AppStore purchased apps, and it 'sticks' across shutdowns and restarts.

Process is pretty simple, I'll spell it out for future reference:

1. Open Terminal
2. cd /Library/Preferences/SystemConfiguration
3. cp NetworkInterfaces.plist ~/NetworkInterfaces.plist.bak - Make a hasty backup in your home directory
4. sudo rm NetworkInterfaces.plist delete the original
5. Restart your Mac
6. Open AppStore and try to sign in. It should work.

Apparently this works because the MAC address is used as part of the receipt/authorization process.

Solution 2:

What worked for me was to go to Store>Sign Out

Once I was signed out, I was able to sign back in and purchase/install apps correctly. Not sure why this happened, but it fixed it for me.