welcome to the forum.

if i remeber right gameguard is an application for playing games like ragnarok online. The mmorpg in question is it ragnarok? I think it has noting to do with avast in this case (could be wrong) but gameguard has to be updated sometimes sens the company behinds it relases updates to it sometimes a months. So have you update it resistantly so you running the latests update. It could be that simple and why you get the error from it.

good luck and let us know how it went for you.