Q: Cannot update in app store

If your Mac is running v10.8.2  as indicated in your profile, updating your system software may help the App store error issue.

Install the OS X Mountain Lion Update v10.8.4 (Combo)

Then restart your Mac and try updating your apps.

If your Mac is already running v10.8.4, restart your Mac then try the App Store again.

Delete this file:

/Library/Preferences/com.apple.SoftwareUpdate.plist

Don't empty the trash for now, just in case things get worse you can always go back to the original.

Thank you Hackintosh. That solved my problem... here's what I did.

Quit Software Update, launch terminal and do:

sudo mv /Library/Preferences/com.apple.SoftwareUpdate.plist ~/Desktop/

Then restart Software Update.