We could not complete your App Store request. An unknown error occurred (10

i got the same error

This happened to me.
What I did was go to Safari and opened Preferences > Security. I then clicked Show cookies and did a search for all cookies with 'Apple' in them. I deleted all of these, restarted the Mac and now the App store functions correctly.

It will probably show you a new T&C for you to agree to before you can purchase anything.

Ditto...

Same for me. Removing Safari cookies didn't help.

I was having the same problem until I removed all of my cookies in Safari as suggested in the post above. This solved my problem.

I am getting this repeatedly. I have restarted the App store many times (not yet my computer though), and tried deleting all my apple cookies, to no effect.

Will restart my mac, and see if that helps.

To fix error 100 in the Mac App Store: sign out, quit the App Store app. Sign in again, try to download an app, accept Terms and Conditions.

Yep, forced to reboot, then re-accept the Terms. Pain in the ***, but probably a bug because the terms borked up when they made an update and refused to activate (The terms popup) correctly.

Same error here. Fixing it required nothing more than a reboot on my end.

Deleting all Apple cookies did it for me. What a pain.

The instructions found at http://igyaan.in/2011/01/how-to-fix-mac-app-store-an-unknown-error-occurred-100- problem/ fixed my problem

Basically, logout of your Apple ID. Quit App Store. Logout of your mac, log back in. Login to Apple ID, and enjoy downloads.

I have been getting the same error for the last 30 minutes. Since going live today the servers are probably overloaded. Samething happened when they rolled out mobile me.