ATV cannot find iTunes library on Windows 7 (but can on guest account)

My ATV cannot find my iTunes library on Windows 7 professional 64 bit (other than occasional random events where it works).

Here's the interesting part: I logged onto the Guest (non-admin) account on my computer and clicked on the iTunes icon to see what would happen. Viola, i could see the ATV icon and select it to play music. I then closed the program, switched back to my usual (administrator level) account, and No Joy.....can't see ATV and the ATV cannot find that library. If i go back to Guest, i can see ATV. I have a lot of music on this computer, but only 4000 songs actually in iTunes, and just a test file in the guest's version.

I have rebooted/reinstalled/checked firewalls/updated all software and so forth. I can play apps, Netflix, etc. just fine from the ATV, and can use Airplay from an iPad's to play any content, and i can see ATV when logged into the router on the windows pc. I've tried the multitude of fixes on apple support.

Any thoughts on what might be interfering with my user account and preventing access between ATV and iTunes in home sharing (my account has full privileges, while Guest account is not an Administrator).