Won't doc or mount on Mac after battery replacement

I replaced the battery on my 20Gb 3rd Gen iPod and everything works; menus, audio through earbuds, etc., but it won't work on my inMotion doc or mount on either of my Macs through iTunes. When I plug it in my Mac via FireWire the screen says it's either charged or charging. Any thoughts as to why? Is a new logic board maybe the fix? If so, how easy are they to put in?

Thanx in advance, Carl.