iMac screen tilt causes machine to shutdown

My iMac 21.5 is less than two months old. When I tilt the screen even slightly (as you're supposed to be able to do) the machine shuts down. Totally. And I can't get it back for 5 minutes (today I timed it!). This can't be right. I can't find anyone discussing this and as it's the Easter weekend here, telephone support from Apple is not functioning.

I'm going to call Apple on Tuesday after the holiday, but I'm really worried about this. This is my first Mac and it's really precious to me!

Has anyone else had this problem and are there any solutions?

Thanks in advance.

worked this out

Somebody on Apple support forums said to check that the power cord wasn't loose. So I tilted again and watched the power cord. As it tilted, it threw the power cord loose enough for the power to cut out and the machine to shutdown. As long as I held the power cord firmly 'in' with one hand and tilted with the other, no shutdown.

You'd think a power cord should be immune to a few degrees of movement, wouldn't you? Good grief.