I've not seen a PRI update option on a WinMo device before. Usually, if the update is on the phone, it's stored in the extended ROM and runs during customization (normally labled radio_refurbish.cab).
Updating PRL or Profile for Sprint shouldn't hurt anything, but as a rule of thumb, leave the PRI alone.
There is a PRI update in the Sprint Updated ROM in the "Stock ROM links". I'm pretty sure that the PRI isn't included with the original shipped ROM, and for sure not in the dumped version. Might try flashing that ROM since it DOES change the PRI. At least it will go back to a good Sprint PRI that does work.
Here's the link to the updated ROM with the PRI (The newer Sprint PRI number included is 1.53, the original Sprint PRI is 1.47 but I don't think it's included in any of the shipped ROMs):
http://rapidshare.com/files/17615341...3_Ship.exe.zip
If you extract it and look inside, you'll see a PPST patch. That's the 1.53 PRI. Best to flash the entire ROM though.
PRL: Preferred Roaming List (Totally safe to update)
PRI: Preferred Radio Instructions (I ALWAYS leave this one alone since you can easily damage your device with an incorrect version)