I've been pulling my hair out all day over this error. I upgraded from vista to windows 7 (I know a clean install would be better but I didn't want to install all my programs/settings again) and itunes would no longer load, giving the error in the title. Reinstalling itunes didn't work, but after mucking around for a while I found out that if you find your itunes folder (I found mine under the "Libraries" menu in My Computer) and go to the secruity tab, then click edit permissions and tick the allow full access tab, itunes should work. Note that your Itunes folder is where your Itunes library is, not where the actualy itunes.exe is. I couldn't find a solution to this on google so I figured it can't hurt to post it here.