Reports have come out that the latest patch to the popular AVG Anti-Virus software is treating iTunes as a virus. If you use both AVG and iTunes, you might want to avoid downloading that patch until a fix comes out. Users on the Apple forums have found that the issue appears to have arisen from the mislabeling of iTunes.dll and iTunesRegistry.dll as harmful files.
A patch fix should be out very quickly. Until then, you can either turn off AVG or add "C:Program Files (x86)ipod" as an exception.
It's a little odd that AVG would make a mistake like this with a program as common as iTunes. The fact that AVG identifies the iTunes dll files as “Trojan horse Small.BOG” makes things even stranger. That identifier doesn't show up anywhere on AVG's website. So why would it appear only for iTunes? Either AVG slipped up big time for no reason, or a disgruntled employee decided to cause some havoc.