ITunes keeps asking for my password

Question

First, it's important to note that what I'm about to describe is happening only in my MacBook Pro account, not on my iMac account; nor is it happening on my wife's MBP account, nor on her iMac account.  In other words, it's highly probable that some (inadvertent) action of mine has actually enabled this annoying 'feature' of iTunes.  I just can't figure out what I can do to stop it.
The Problem:
For the past couple weeks, the iTunes application on my MacBook Pro has been displaying (intermittently) an alert to notify me that I need to enter my User Name (supplied) and Password (which I must enter manually) so that it can continue to make "authorized downloads."  Interestingly, iTunes displays this notice irrespective of whether the application is even running at the time.   I understand that iTunes may need to check in periodically (in the background) with the Apple Store, but I can't figure out why it is no longer able to do this without my authorization every single time.  Here are the steps I've tried so far, to no avail:
a.  iTunes Preferences > General > Check for new software updates automatically (turned off);
b.  iTunes Preferences > Store > Always check for available downloads (turned off);
c.  iTunes Preferences > Store > Automatically download pre-orders when available (turned off);
d.  I have signed out of the Store, Quit iTunes and Logged out.  Then I logged back in, opened iTunes and Signed In to my account again;
e.  I have selected iTunes > Store > View My Account and turned OFF "Recommendations and Ping Posting;"
f.   I have selected iTunes > Store > View My Account and clicked the button to "Reset all warnings for buying and downloading;"
g.  In the very alert containing my User Name and Password I have checked the box beside "Remember Password;"
h.  About 10 minutes ago, I opened iTunes Preferences and in the Advanced pane, I clicked on the Reset warnings button beside "Reset all dialog warnings." If this most recent effort finally does the trick — I won't know for sure until several more hours elapse — I promise to log in to let everyone know.

Answer 1

UPDATE 2:  As promised, I am writing to let everyone know that I believe that I finally may have resolved this problem.  The procedure that seems to have resolved the issue on my computer was one that another user, Mandoskier,  reports having resolved the same problem on his computer (https://discussions.apple.com/message/17276790#17276790), in which he reported the following:  "This problem was solved for me by trashing "com.apple.iTunes.plist" from userid/Library/Preferences folder and repairing disk permissions."
I trashed that file two days ago, and also repaired disk permissions (using Disk Utility) and iTunes hasn’t once asked for my password!
May not work for everyone, but it’s worth a try if you haven’t yet given this recommendation a shot.  Good luck, all.