Hi dcubert,
I have seen that issue before when the boot order changed on my servers. To boot into Automation the NIC must be in the IPL Boot Order BEFORE the hard disk, this way if Altiris ever needs to boot the computer into WinPE for example it can do so.
There are other reasons why this may occur so if you are still having trouble update this post with some more info and we can take a look.
Regards,
Mark.