use this procedure at your own risk, although it worked for me:

to move from ROW 1.12 to Cingular 1.12:
sync your treo first
if you have a backup, you can do a hard reset before you proceed
use tokenwriter to reset the crnm to CNG
run the windows rom updater
when it tells you to sync to back up and install...don't sync
instead, copy all the programs in the desktop install folder to the palm\launcher folder on the treo---then cancel out of the installer program
run the updater program from your card, making sure you have sufficient memory, etc.
when it tells you it cannot proceed, since rom is newer, take the treo out of the cradle and do a soft reset (pin)
after the reset, there will be a new app call DC on the launcher, run this
this will go through the rom update
when finished, either restore your backup or (preferably) reinstall programs from scratch. If you restore a backup, you should probably not reinstall the network files, or the current carrier db, since these may have changed. I don't know about this for sure, but I did not reinstall those and it worked fine.