nomis5 - 3:18 pm on Mar 23, 2011 (gmt 0)
It may be nothing to do directly with India. It could be that the drop in your traffic caused the price of your ads to go up, this is not uncommon. It is one of the reasons that there are often discussions here about how many ad units to have per page. Sometimes, less is more.
So investigate very carefully about excluding Indian traffic altogether.