So how long has it been since there was a Red Ring of Death thread?

I've had my 360 for about five years. Its been sitting vertically in the same spot the entire time, until two weeks ago when I rearranged my entertainment center and laid it on its side. It has never had a glitch the entire time I've had it until last night, when it cut off in mid-game (after @two hours game play) and gave me the "overheated" pattern. I shut it off and didn't turn it back on until tonight, but after ten minutes of play it did it again.
Any ideas on what the issue is? Might I have jarred the solder connections when moving it? Is the airflow that much worse in the horizontal orientation? Is it more likely to overheat again once it does it the first time? I don't relish the idea of losing my info if I have to get a new unit.

Thanks in advance...