display goes black

I have OSX 10.8.4 on MBA. Every once in a while I face this but I am not able to find a pattern yet.

When it happens, the screen is active (not in sleep mode) and the moment I click (e.g. a hyperlink in Safari), it goes black. It would come back on its own in a few seconds.

I have checked there are no hot-corners or magnets nearby.