Sorry for the late answer.
Printer is connected with USB.
ATI Graphic driver is 6.xx
About the "Hosts" part : since he had it translated in french for some reason and it seemed like it was 100% equal to the one on my computer, I copied it. However I had stoped him from reading everything at the 127.0 line. And actually it was the last one for him but (since I am on Vista?) I had the extra "::1 localhost" line. He does not have it.
Now I think it is unfortunately time to give up because as expected he does not want to uninstall the printer since it was very hard to install and while I am 100 % ok with you calling me a newbee, he is a super newbee and it took me like 30 minutes to do something which should take 3 (posting pics of the screen for example) so it is to heavy to handle and unfortunately I do not know how to take control of his computer (it would be the solution) and it seems too complicated from what I have read on the web since I need to set up things on his computer also before beeing able to take control of it
Thanks a lot for your input and time invested. I wish we could have solved the problem but as suggested it seems to be a wider problem than just a Avast related problem.