Maybe you're running a game that requires the 3.0 software update and you're not running that software version? If you've got an iPod touch you may need to pay a small fee to update to this.
and for anyone who says that its a rip off that ipod touch users have to pay for the software updates whereas iphone users get it for free, if anything iPhone people are paying more for the update as we pay for it through our (expensive for what we get) monthly bills.