Got my AVIC-X910BT about 11 months ago. First thing I did was to mod it with all the navigation upgrades (used Diaftia's mod collection). First step of the mod is backing up your current system files...just in case. Mod complete, and everything works awesome.
Fast forward 11 months and all of the sudden my unit reboots itself while listening to music on an SD card. The unit then continuously reboots itself every 30 seconds never making it past the splash screen. Hitting reset doesn't fix it, and neither does restarting the car. Hitting Reset + Eject temporarily fixes it, but navigation then doesn't work and the issue represents itself the next time you start the car.
Called Pioneer. They say that a file got corrupted while I was listening to music. Not too uncommon. They want me to send the unit back to them so they can reinstall the software. Turn around time is 3 weeks...so no car stereo for 3 weeks. Plus I gotta pay shipping. One more month and it would have been out of warranty, so I would have had to pay for the repair too.
Then I remembered the backup I made. So, I hacked into the unit again, restored my files (including the mods) and low and behold everything was good and back to normal.
Now, you might think that the mod caused the issue, but I highly doubt it. This same thing happens to people that don't mod their units. Only they don't have a system backup, so they're screwed. Also, all was good for 11 months, and then suddenly things broke while using features of the system unrelated to the mod.
So, point is, if you got a unit, highly consider hacking in and at the very minimum, grab a backup of your files. It's very easy to do, and in my opinion, totally worth it for this reason alone.