I had the same problem which appeared when I bought an iPhone and synced it for the first time, which required an update to the latest version of iTunes.
The first sync seems to have automatically enabled "Share my library on my local network" in the Sharing tab of iTunes Preferences. The Sync app has also caused a number of other apps to slow down or get buggy that have nothing to do with the IPhone (legit, robust, professional apps like Adobe CS and Avid).
At any rate, I disabled wireless sync, deselected the library sharing option, and now iTunes launches dialog-free and my pro apps are behaving normally again.
Of course, now I can't share my library on my local network or sync wirelessly, which are supposed to be key value propositions of these products.
I ran into this problem updating a dusty old 32.bit Hackintosh OSX 10.6.7, updating from iTunes 10.1.1 to iTunes 10.6.3. Googled the error message, and found this thread, but I think I found the easiest fix, and I will share:
Close your problematic copy of iTunes;
System Preferences > Security > Firewall > Advanced (unlock and authentication probably required);
Delete the iTunes reference reference using the minus - sign method;
Add/Navigate to your new installed/updated copy of iTunes using the plus + sign method;
Repair permission and restart your Mac:
New version of iTunes should work now without pesky repeating authorization request
It looks like previous version of iTunes was referenced in Firewall > Advanced,
and everytime new install/updated iTunes was launched, accepting the incoming connections message would not correctly reference new iTunes, but still reference old version number as a bug...
Worked for me right away, simply, hope your problem is as easily fixable
FINALLY! Found something that worked for me. I'd note though that it says to "move to desktop" but instead you just copy the file out and delete whats in the preferences folder.
I also had to delete "com.apple.alf.plist.lockfile" and "com.apple.alf.plist~orig" to make it work. Deleting just "com.apple.alf" only worked for one time before the problem came back.