My guess is that it's bombing on your ReplaceTokens task. For some reason, I could only get it to play right if I didn't use explicit pathnames.
For example:
# ReplaceTokens ./images/Sysprep/cmh.inf ./temp/%COMPNAME%.txt
Works just fine. the ./ is simply /mnt/ds/
I couldn't get it to work right if I was keying in the full /mnt/ds/images/Sysprep/cmh.inf.
We were also having the issue where we'd get CIFS errors when the script was finished running and the machine would reboot. I recently applied the update from Altiris KB 34859
https://kb.altiris.com/article.asp?article=34859&p=1 and now the machine properly restarts after running the script. We're running DS 6.8 SP1.