There is an interesting read in PC World regarding serious security leaks in some of the most popular AV programs like Symantec, McAfee, Trend Micro and F-Protect.
Some apparently have been fixed, others not yet . The gist is that the progs set on automatic update were only getting updated definitions and not any updates to the engine itself.
A way was found ( of course ) to bypass the protection and do some nasty things to your PC.

An article by Stuart Johnston discusses these problems and there are links to the various sites to get the updates. It also mentions what the latest builds or versions are for these progs. You have to also allow for the for the time lag between writing and publication of these articles.

Take at look at : PCWORLD

Make sure you are OK and updated.