It is a 'notification' only something is accessing the avast registry key with write permission and avast's self-defence doesn't allow that and downgrades the access to read.
These pop-ups are suppressed but for some reason on Vista SP1 this suppression doesn't seem to work, this is in hand but I have no idea how long this might take to resolve. Though the main thing is that there is nothing to be concerned about and nothing that you can actually do to stop them or whatever it is that is the cause (write access to the avast registry keys), so there is nothing to be fixed.
A forum search about this will reveal a number of topics about this.