Yes, it's ATI Radeon HD 6250. Sorry for no detail. Any solution?
BTW, only with Zenwalk and Salix I face this. But I like Slackware-based, especially Salix, which is more responsive than other distros with MATE or Gnome, even some Xfce ones. So, I'll keep up with Salix but will never do a logout , unless I get a solution. Thanks.