I used to use PwnageTool all the time to help get me into DFU on my 3G. Fire up PwnageTool, click the DFU icon and it would take me through getting into DFU mode.

But now no matter what I do or what Mac I try PwnageTool on the DFU button is always greyed out and I'm unable to click it. I've tried two Macs at home and one brand new iMac at work - all running Snow Leopard.

Have I missed a system requirement? Does this feature not work any more?

Thanks in advance,