You guys might want to check your numbers from 8/21/09. On one of my accounts, Yahoo charged me $90.00 for a SINGLE click, $45.00 each for multiple clicks, and so on. This was for content traffic. The kicker is my MAXIMUM CPC for content is 10 cents.
I sent a message to Yahoo and hopefully they will have a satisfactory explanation but you should check to see if you got killed yesterday.