I am having the same 'problem' - but I am not in the least bit worried, I know AVG is still doing its job. The reason for the so-called problem is no doubt purely down to everybody trying to update at the same time. I shall just try every now and then until mine completes, I am sure it will be alright on=the-night as they say!!
There are some very large updates to download today, amounting to some 4.6Mb when I started! As someone has posted above it is the AVG server which is being overloaded and although the download started at its usual high speed, it faded away to under 9kbs, and then failed.