Since some months ago, we started noticing something odd in a lot of computers of our network (with xp) , when we do right click->runas in any exe and try to run it as administrator, it complains saying "unknown user or wrong password". If I try it in a cmd, runas works right. (with the same user and password). If I try a domain admin account (or any domain account) it works ok.
¿Could it be a GPO config that someone changed?