Both names are name for different framebuffer - problems with framebuffer may give blue screen or scrambled screen.
You dont need NATIT anymore (often also makes problems!). Delete it if you have it in extensions.
You can add ETHERNET Device which fixes TIMEMACHINE , then add 3850 MEGA.... Grafik Device and let the tool create your efistring in the boot.plist.
I tested both with 10.5.6 :
Timemachine now works again (with orig. newest 10.5.6 IONET...kext) and orig. newest OpenGL/ ATI 10.5.6 drivers.
HINT: The new great pcwiz UniversalInstaller has a bug, cant make both EFISTR TM_FIX+ EFISTR GPU. It only creates one string, even both sould be created.
Attatched EFISTUDIO_EXTENDED .sitx.zip (smaller) / also as .zip (small)
EDIT: May also work for ATI 3870 (also use 3850 Megadlon Selction)
DL today didnt work. Tried to upload again - not working. Must be a problem of the forum !
I will upload it later again.

