In case you do do an update to an 11 at some stage, here's a link to instructions on getting past a Kaspersky-related install error. (Not especially common as far as I can tell, but just in case ...)
You're probably already done it, but if not I suggest you exclude your library folder from AV scanning. AVG seems to be involved in most of the recent "vanished library" threads, but not all. As far as I can tell iTunes gets tripped up in the act of saving a new temp. copy of the database and then renaming it as iTunes Library.itl. AV is the most likely candidate I can think of for interfering with file operations.