You do not have enough access privileges for this operation!

I can also add something else. In the past, when something funny happens in iTunes, I've had success by deauthorizing my computer and then re-authorizing it. I tried to deauthorize my computer and got the following message:

"There was an error storing your authorization information on this computer. The required directory was not found or has a permissions error. Correct this permissions problem and try again, or deauthorize this computer if the permissions cannot be changed."

I get it repeatedly. As I said above, I've checked and/or repaired all my permissions. This happened after the updgrade to 10.4.1.

Solved. Hope this helps someone else. Somehow my Shared folder (inside Users) got deleted. Don't have a clue how it happened. Without that folder, iTunes can't authorize or deauthorize a computer and it resulted in my error message.

I found the answer in the following Apple knowledge base item:

http://support.apple.com/kb/TS1277

There are clickable links for Mac OS X and Windows. Follow the instructions. It provides terminal commands to create a Shared folder and to set the correct permissions for that folder.

The Shared folder is at the following path: <BootVolume>/Users/Shared

But be advised that there are several reasons you might be this error message and not having a Shared folder is just one of the reasons. If you do a Google search for [iTunes "access privileges"] there are reports from a variety of individuals that note a variety of probable causes.