flashing official RUU to restore phone (or something?)

[JesterJay]

Okay, so before I say anything else, I'll say I'm a complete noob to this; I'm just trying to verify what I've gleaned from a a few hours of frantic research.

So, I recently bought a used HTC Thunderbolt (S-off with 4ext recovery), and it works fine, except for just a couple hours ago, it rebooted itself and came back with a screen that said:
.

Finding update package...
Opening update package...
Installing update...
assert failed: check_cid(getprop("ro.cid")), "00000000" , "11111111" .....
"99999999", "VZW__00`") == "t"
E:Error in /cache/fumo/OTAPkg.zip
(Status 7)
Installation aborted.​

.
Since then, I haven't been able to get it to stop doing that, so I've been looking around trying to find a way to fix it, or at least make it usable. And I think I've come up with something; I just want to check here to make sure I won't be colossally screwing something up, or if someone has a better plan, that would be great, too.

So, from what I've read, I should be okay if I flash an official Android RUU by adding it to the SD card with my computer then putting it back in the phone and using "install from sdcard".

Is this right? An answer ASAP would be greatly appreciated.
Thanks

 

[JesterJay]

Nevermind, I think. I did a factory reset/wipe through the 4ext and it seems to have fixed things.

EDIT: Okay, so doing that was really just a temporary fix, it seems. The update dialog box came up again, and thinking something different would happen, I allowed it to update, and got the same issue.