Which version of LDMS are you using? Were you able to get the ldprovision.log or the hiiclient.log from the failed machine?
Have you consider using Jan Buelens Hardware Independent Imaging method
I too have issues running HII task. I changed the HII to use the UNC to download the drivers. But what I noticed is after I schedule the task to run, it works fine the first time its scheduled. After that I have to go in to the template and delete and re-add the HII task to the template. If not, it will fail everytime. I'm using LDMS 9 SP3.