if ur talking about beside the search results and not at the extensions column of google chrome, yes, i also have the issue of it coming and go as it likes.
nope, i checked it is not linked to cloud services streaming connection (my's enabled but not connected now but webrep is showing beside search results now)
chrome v18 latest stable.
i will wait till the next minor release of avast to see if the problem is solved. there are some other more significant problems with a few win 32 bit xp systems having driver lock ups with avast driver. (a downloadable temporary fix has been released but they are gonna update the drivers for a permanent fix)
dun bother to try reinstalling avast cleanly or webrep for chrome, i tried it and this minor problem remains.