Monitor Failure

Sometimes when I’m playing Gmod I’ll freeze up for a second as if I’m about to crash, then my monitor turns off as if it’s gone into stand by. (Like, the green light goes orange, I can still hear music from my earphones which are connected directly to my tower.) Then I don’t really have any options but to reboot my computer. Any suggestions?

2.2 GHz processor
1GB RAM
2600XT graphics

Thanks

OK, sorry to bump, but does anyone have any idea?