For most people it isn't a problem and is often an issue of conflict with another service, etc.
avast has a fast start to give protection earlier in the boot this may mean a service isn't available at the time update is attempted. However we can delay the check so any possible conflict shouldn't be an issue.
You need to edit the [InetWD] section of the C:\Program Files\Alwil Software\Avast4\Data\avast4.ini file and add the following line (depending on your connection type enter one or other of the Bold lines below):
Broadband connections, add this line:
AlwaysConnectedWaitSeconds=120[InetWD]
AlwaysConnectedWaitSeconds=120
The figure is seconds and the above equates to two minutes, you could try that and adjust upwards if required, 180, 240, etc.