Seriously, if you ever get a definitive answer, let us know.

All we can give you here is unhelpful speculation but one time or another we have all equally suffered.

If everyone has had this happen, then I guess it's not some kind of punishment. But it's just weird. My clicks have been paying $1 to $3.50, so to see 3 cents is shocking.

Lots of things could have happened. Google rotates ads through all the time to see how they'll do, so some low paying ones could have been in place and someone clicked on them. Your high paying advertisers could have exhausted their daily budget, and ads are turned off until the next day. The highest paying ads are typically the first ones that load on the page, but maybe you got some clicks on some of the last ones that load on the page. There may be some smart pricing going on. I believe Yahoo accounts for the source/quality of the traffic when figuring out how much to pay for a click; maybe Google does too. If the clicks were from a different country or source, they may have discounted them for that.

You're probably never going to know for sure. Is this a one day occurrence? If it happens for a couple of weeks - then I'd start being concerned.

I know some days, some of my sites will have very low revenues, then it's back up to normal the next day. My take on it is Google is rotating some advertisers, tried one that ended up performing very poorly, and took it out the next day, until they increase their EPC. Google needs to test and evaluate advertisers before determining the minimum EPC they should pay, based in part on their CTR on your site. It's part of the game.