uuhhhh... okay. I remember I had this happen a few times when I first did that to get the iphone dock, but I'm unsure of how I fixed it.
I'm assuming you went in and either manually changed the dock, or you had an application such as customize do it for you. Try changing that back. and then in the new preference say to use the old dock and then relaunch the springboard, or restart the iPod and see if that helps.