Hey Jesse025
I too had the same problem with ProDesk 600 G2 and EliteDesk 800 G2.
Fixed it by using the HP WINPE 5.0 driver pack found here:
http://ftp.hp.com/pub/caps-softpaq/cmit/HP_WinPE_DriverPack.html
Randomly, the NIC driver is the same version and same PNP ID's. But this worked for me.
Try stripping your PE boot image back and only using the above driver pack by using selection profiles in MDT. Will work with all 600, 800, 1000 Desktop and Notebooks.
Good luck :-)
MikiCJ