Might be your data plan is too less (KB) or free trial period might have ended.
When I check my balance, I see my volume balance is 1048576, which I guess means 1 G. My validity is till 22 February 2013.
It seems to be a common problem with Idea. I found many such complaints online.
Idea 3G Nokia bundle offer - Free 3G Pack Activated But Balance Deducting
One of my number (reserved number) has been deactivated despite I topped up with "up to 6 months validity" recharge coupon (number would be activated for 6 month without any use till 6 months).
Validity of a lifetime SIM can last for mere 20 days - daily.bhaskar.com