Each time you play a file or update tag information the iTunes library needs to be updated. As far as I can tell this is done by copying all the information into a new, temporary copy of the database, then deleting the original file and renaming the temporary file to take its place. If "something" latches onto the temporary files iTunes can process them properly. Typically I'd suspect anti-virus software or the Sony VAIO content manager, but since this is a Mac neither should apply.
If might indicate the hard drive isn't as responsive as it is supposed to be, in which case make sure your backups are all up-to-date.