Ok so I have a bit of an odd problem. I decided to get my Xbox 360 out for the first time in about four months, it had been sitting under my bed. I set it up in a vertical position and went to switch it on and nothing happened. I thought maybe RROD had hit me at somepoint and I missed it. Anyway, I decided to try it again but instead of vertical I decided to flip it to horizontal. This time it worked, I have no idea why. Anyway I decided to try it in vertical again as I want it set up that way and it didn't work.

I've tried it a few times and it only seems to work in a horizontal position, I have no idea why this is happening. This officially has me perplexed, anyone else ever seen this?

it could be that the power plug in to the mobo could be coming loose? i have no idea

Most perplexing, Lt Commander. Maybe Spot has bitten the cables.

Or:
AV cable may be at an angle and not sitting quite right??