Tequila Republic

I have a friend who is using the current Viewer 3 sl viewer. When he chats in private AND in general chat all his posts come through double. Also when he buys things or gives someone lindnes he ends up having automatic double transactions. He has tried different viewers and had the same issue. He has also unintalled everything SL and completly wiped it from his computer and redownloaded the software... still having the same problem... HELP?!!!