I FIXED IT!! I can't believe it . I actually figured out how to make it work(well sort of). My Apple Software Updater now works (almost) perfectly and I just successfully downloaded and installed itunes 10.6.3.25 through it!!!
Ok , the way I see it, either the latest itunes update or the recent Windows Patch Tuesday on June 12th, 2012 must have inadvertently removed the Administrative Rights from the Apple Software Update Tool .lnk file.
So you must go to where the file resides on your hard drive - for me that was C:\Program Data\Microsoft\Windows\Start Menu\Programs - Right click on the Apple software Tool icon and choose properties. Click on the compatibility tab. At the bottom of this tab click on "change settings for all users" and hit Yes at the UAC pop-up. Now make sure you place a check in the "Run this program as Administrator" under the Privilege level section at the bottom. Hit Apply and then OK. The hit Ok again to get off the properties pop-up.
When I went back and clicked on the Apple Software Update shortcut, I got a UAC pop-up asking me if I wanted to proceed(something I had always, in the past, gotten but haven't since this problem started). The Apple Software Update tool came up and to my suprise the progress bar STAYED and started to slowly fill up partially with the green progress bar. Viola, the itunes 10.6.3 update showed up on the top part of the screen as a new update needing to be installed - the bottom screen, as usual, had the changelog info for the 10.6.3 update. I clicked on install and , again, Viola. the update downloaded and installed flawlessly. I had to reboot my computer and when it restarted, itunes was working perfectly and it was correctly showing as itunes v10.6.3.25.
I say it is almost or sort of fixed because when you click on the Apple Software Update shortcut after the 10.6.3 install it goes back to doing the same thing it did before(i.e. processing for a second and then saying there are new updates but showing a blank field). Maybe this is the way the software now looks if there are no updates available to install - maybe Apple is working on this to eventually get it back to normal. All I know is the process I outlined above worked for me(at least to get the ASU to recognize and properly download and install itunes 10.6.3). It's certainly not perfect, but it worked. Please try this method and let me know what results you have with it. Good luck.