Not enought juice
Last night I was trying to rip some tracks off of an audio cd to mp3's on my carputer using CDEX. I didn't have the truck on just in ACC. I use an ITPS w/ PW70A. The DVD/CDRW would start ripping a track then all of a sudden my Lilli would just totally lose power and about 3 seconds later the PC shuts down. I powered it back on, went through the same process, and it happened again.
This happened about 3 or 4 times until I said screw it. It would never rip more then one track before shutting down.
You might be drawing too much power. Hook your computer up to hosehold AC and see if it still happens, if it does more then likely is a power problem.
It's probably the ITPS trying to regulate to 60W power, and the drive is just taking too much power from it. Or, if you've bypassed the regulator on the ITPS, it could be that even the PW70A isn't supplying enough power.