Avast 4 Pro Desktop Icon

Hi, been using Avast 4 Pro for a couple of weeks and find it a nice AV product and very pleased with the way it works. However something strange happens to the Avast Desktop Icon. Every so often it changes to a “unknown application” Icon (white square) and the name become a “~”. I’m using Win XP Home Edition with SP1 and all other crittical updates, all drivers are also upto date.
It’s not a big issue but a little weird none the less, anybody have any ideas as to what may be the cause?

TIA,
Trev