Target Disk compatibility Issues between the two Macs?

I recently acquired a (free :) 1.2 GHz G4 12" iBook(v. 10.4.11), that has a blacked out screen. I'm pretty sure it is an inverter issue because I can see and some what navigate the computer from a very faint image. I do not have an external monitor to connect it to, so I figured I'll boot it from my 2.4 GHz (Penryn) MacBook 13"(v10.6.6) via Target Disk Mode to confirm my hypothesis and see what kinda shape the rest of the iBook is in. My Penryn does not recognize the G4's drive and vice versa, It doesnt even appear as a mountable drive in Disk Utility on either one (both of the Macs do successfully mount other types of external drives). I've tried several different firewire cables to no avail, and both Macs do successfully boot in Target Disk Mode. So either both of the Macs have the same issue of being unable to mount drives through Target Disk Mode (highly unlikely) or Apple dropped backwards compatibility between v.10.6.6 and v.10.4.11. Anyone have thoughts, explanations, or theories to address this issue before I start tearing down the iBook and possibly wasting money on parts I may not need.