Deleting the partition table of your ipod will mean your ipod is unable to boot. Â Not quite sure why you assumed that this would be the right way to reset your ipod to original settings. Â The ipod needs to be able to boot up, so .. ? So what's wrong with it is that you did something unreasonable to your ipod.
This isn't really anything to do with Rockbox, though, right? If I took a non-rockbox iPod and deleted the partition table it would probably behave in a similar way..
Try using Apple's tool to reset your ipod back to factory settings.