now for something totally different: update problem

[Lupadime]

I have been trying to upgrade to feisty from edgy. The update wizard starts but then tells me:
upgrader application not verified. After pressing ok the wizard closes.
What gives. BTW in my adept the upgrade button has always been locked down so I don't have the option of using that.
Would appreciate any hints. Been using kubuntu for a while but still very much a newbee. TKS