[FlyingShawn]

I didn't rename it, but I've since been able to figure out a fix without the JTC program. Ziggy's Excel method wasn't working for me (I think Excel wasn't saving the format correctly) either, so I worked out my own method using Notepad.

For those curious:
0)I'm using a Sprint Mogul, so I first ran the HTC official fix to correctly date new messages and keep me from having to do this all over again. Anyway, onto the instructions:

1) Extract the .csm per Ziggy's instructions (to save time, I only backed up the text messages in that .pib and backed up everything else in another backup)
2) Open it in Notepad instead of Excel
3) Do a Find & Replace to change all 2016's to 2010
4) Save it using Unicode Text (it might have given the file a .txt extension, I don't remember, but if it did I just renamed it to .csm)
5) Upload it back to the phone and restore using PPC PIM Backup (don't bother putting it back into the .pib, PIM Backup can restore directly from the .csm file)