SCCM OSD Task sequence fails only on optiplex 740

I have a task sequence that deploys windows 7 enterprise and has been working well for a long time now, almost 2 years. a colleague came to me recently with a batch of 740's to image. i fired up the TS and everything goes fine until just after the "setup windows and configmgr" step. that step completes and the sccm client gets installed, however as soon as it does the computer reboots. an examination of smsts.log reveals that the TS engine cannot find the TS environment to go on to the next steps of the TS, and reboots, leaving the computer half deployed. this very same task sequence works, and has worked for nearly 2 years,without error on 755's, 745's, 960's, D610's, D620's, D630's, E4500, etc.. you get the idea... the only perceptible difference is that the 740 has an AMD chip. so i've updated the bios to the latest, from june, 2.2.5, built and captured, with SCCM, an "AMD Image" of 7 Enterprise, and it still bails out of the TS at the same place. Any ideas? why can't it find the TS environment when i can browse to the folder and find it myself? it's been booted to the installed OS and executed more than one step in the TS by this point, why does it forget after instaling the client? what's so different about the 740?