If you have updated AVG to the latest version available during a local scan, your antivirus may indicate the presence of a Trojan inside the iTunes directory, viewing the file catalog iTunes.dll and iTunesRegistry.dll as Trojan horse Small.BOG
The problem, however, was found by many other people and also the Apple support forum is full of similar reports. If you use Windows, and have encountered the same problem, the only remedy while waiting for a patch for AVG , is to delete the iTunes directory from scanning.