New Steam Client
I have the new steam client. Everytime I try to play MW2 with VAC Chaos. VAC Chaos gives me an error "invalid steam client" and then exits. I have VAC Chaos 2.03.
I don't think you should use it till it will be updated..because u might risk a ban.. and by the way..it worked for me few days ago.
Try This
run as admin on steam
and then run as admin at VAC chaos*well while u want to login*
and there u go