ardvark,
Do you mean that Avast starts to "seek" a server connection before your dialup is finished? How did you determine this?
As far as I know, you cannot delay Avast's update process, only stop it from automatically downloading the updates. Normally Avast will wait for an internet connection before starting the update process.
You can set Avast to "manual" update if you wish. That should stop the error message, but you would loose the benefit of auto-updates.
I believe that you have other problems causing this.
What version of Avast are you using?
What update is listed in the About section?
Has the updater function working correctly before?
I'll be here.
techie