Whilst the avast icon is rotating and is reporting your system is secured. The Summary screen also shows secured. But if you open the Real-Time shields and check them there is zero activity displayed.
This is the same on both my systems XP Pro and win7 32 bit.
I have just done an eicar test and the alert function is working, image1. So the Summary status of Secured appears to be correct. But no activity in the actual interface for the Last file infected: field. In fact both these last scanned and last infected fields are greyed out in all shields, image2.
It appears to all intents and purposes that you are still protected, but the reassurance of having those stats to show it is actually scanning is something which we have all got used to.
I would think that they would pull this update whilst investigating.
glad to hear than that we are being protected but the activity in the shield not running is gonna cause some people to panic thinking there anti-virus isnt working fully.