In my experience in flashing Blackberry's to Cricket service, I have only been able to flash the Pearls, Curves, and the Storms with the newer version of QPST.

When I have tried it with the older models such as the 8703 and 7103's it has corrupted the SPC.

However, on the older models, I always use the QXDM or CDMA workshop to flash the PRL to the phone.

There is a solution out there somewhere to fix this problem however, it hasn't been posted.