Apple yesterday released a major update to their Mac OS X Snow leopard whose version is 10.6.6.This update also introduces the long awaited Mac App Store.But some of the user who updated their Mac OS and then tried to buy an app from Mac App Store got an error showing “We could not complete your App Store request. An unknown error occurred”.But you don’t need to worry about this problem because it has a very easy fix.
Just follow these steps to solve this issue.
Sign out from the Mac App Store by accessing the “Quick Links” section in the Mac App Store homepage and clicking on “Account” and Sign out.
After signing out, Quit [Command + Q] the Mac App Store application.
Now Log out from your computer and Log in again.
Open the Mac App Store, sign in with your Apple ID and try to download a free app (e.g Twitter). When prompted, accept the Terms and Conditions when asked. After that, the download should start.
Another thing to notice is that if your logout doesn’t fix till now then you should try resarting your Mac.