No, repair won't fix that problem. I've been there, done that... see here:
http://forum.avast.com/index.php?topic=10592.0
It doesn't have to be same like on my system, but if you have SpySweeper installed, that thread I gave you link for, is exactly what you need to fix your problem. See my last reply in that thread...
Cheers !
You were correct, repair did not fix it.

. Although the Avast log said that it had (in their words

) "Done something" to the Ashdisp file.
After checking and not finding any other cause on the machine (worrying, I like to know 'why' things happen), I did a System Restore and this brought the icon back.
I had seen the thread you mention, however it is still a mystery because I have never had SpySweeper installed

Thanks for your input anyway.
W.