Well if you look at my signature you will see that I have XP Pro and avast 6.0 and whilst I no longer have the webrep installed on IE8 after testing it worked (which it did) I removed it as I don't use IE as my primary browser.
In your search results, whilst it might not show green bars it should show at least grey bars.
For this I installed it from the avastUI, Additional Protection, WebRep and that succeeded. If it doesn't and you don't see the avast! WebRep listed in the toolbars (see image1) it isn't installed.
Try the above to install it from within the avastUI - If that doesn't work check and ensure that the option to have the Web Reputation plugin checked. Same drill as for Repair but this time you are looking for Change, add remove programs, avast, Change/Remove, from the next window select Change, and ensure the Web Reputation plugin is checked (see image2), if not check it, clock Next and OK your way out.