This is a long shot, but maybe this might be your situation. At my workplace the IT department backs up everyone's "My Documents" on their server to avoid people freaking out when they do something stupid and lose all of their data. The default location for the iTunes folder is in "My Documents." I could access iTunes at work, but whenever I was at home, I'd get a "locked disk" error message whenever I tried to launch iTunes. The only way that IT could solve the problem was to exclude my "My Documents" folder from being backed up on the server. Actually, that's okay with me. I'd rather not have my employer have a copy of my personal stuff on their server. In one instance that I know of, they searched an employee's backup to find the data to fire him.
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