Screen sometimes flickers black . ..?

[DecoY]

hello. this happens really rarely but sometimes, my screen will go black for 2 secs then show up again. it's kind of like the moment when you install winxp and it's initializing devices and your screen goes black for a sec. i'm not sure what the problem is. could it be power suppply issue ? i've got a 350w fortron 2600+, but should be sufficient