I've been frustrated the past week or two with DS 6.9 SP6 and WinPE4's missing environmental variables, specifically the ALTIRIS_PXE_CLIENTMAC variable which works great as a unique identifier when backing up computers through PXE. Looked into the problem and the issue is that the startutl.bat located in Bootwiz\platforms\Winpe4\%PROCESSOR%\Templates specifically checks for WinPE 2 and sets /opts for that. WinPE 3/4/5 will successfully use the WinPE 2 flags - and I've done it with all 3 of those versions successfully in DS 6.9 SP5 - but apparently the default flags that WinPE 4 wants to use are the WinPE 1 version, which don't actually work right with this version.
The solution is to change the is-winpe2 to is-winpe1 and change the if not errorlevel 1 check to if errorlevel 1. To make it more explicit, change:
call :is-winpe2
if not errorlevel 1 set opt=/winpe2
to this:
call :is-winpe1
if errorlevel 1 set opt=/winpe2
Remember to change startutl.bat in both Bootwiz\platforms\Winpe4\x86\Templates and Bootwiz\platforms\Winpe4\x64\Templates; the same change is needed in both places. Save your updated files, regenerate WinPE images, and your ALTIRIS_PXE environmental variables should be back on your next WinPE 4 PXE client load.
Hope this helps some other people out there. And that the file gets fixed for DS 6.9 SP6 MR1.