@rsm: No, a reset only clears settings and the userstore (ie. books). It only manages to 'break' some hacks by cutting access to their resources stored in the userstore, but for all intents and purpose, they're still installed. That said, IIRC, a factory reset should *not* affect this specific version of Yifan's JB. It *will* break mine, on the other hand

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That said, the logs do help! I can see Yifan's JB is still installed, but broken for some reason (you should *NOT* hit a U007 when trying to uninstall it)...
I can also see USBNet is there, so that might be your best bet to investigate. Just plop the usbnet folder from the source package in the USB root, and restart your device, that should restore USBNet to its default status.
Once you're in, check how messy things are in /etc/uks (you might need a vanilla backup of that, one from any kind of Kindle should do), get rid of yifan's JB (see it's uninstall script), install our key manually (see the 2.5-install script in my JB), and that should do it.