Do you have an at&t device? 1.31 and 1.29 sound like sprint build numbers.
At any rate,the same process can be used if you're on hboot 1.44 and the available ruu contains the same: http://forum.xda-developers.com/showthread.php?t=2390821
Just change the build number in the echo command to whatever build you wish to downgrade to,or to a generic 1.00.000.00, then run that ruu.
While the advice above should get you booting,running the older ruu will let you s off if you desire