[datanoise]

I'd assume it's greyed because there is no update to install. Once you are jailbroken you don't need to use it: I don't know what you're trying to do with that. You probably should have stopped when you didn't see the "jailbroken" file to check what was wrong and/or try to reinstall the JB at that point, before upgrading the firmware. Did you install the hotfix once you "installed" the JB?

I also don't understand why you went the serial route from the beginning: downgrading from the menu would have been easier, don't you think so?

If you want to JB in the future, you can now block updates (install an empty folder on root named "update.bin.tmp.partial") and wait until there is a JB for the firmware your kindle is currently running.