I did the 5.1 firmware upgrade in my X930BT ( upgraded to X940BT in Mar 2014)
I used the X940BT 5.1 firmware downloaded from the Pioneer website .
5.1 firmware update removed the USER/PRG.FLG file and put a new navi.exe in /USER/PRGO/APL
After 15 hours of troubleshooting and reading threads in AVIC411 , I am able to implement the safe mode hack
and nag screen by pass hack .
Here are the steps .It worked for 5.1 firmware.
I made the following changes in the navi.exe located in /USER/PRGO/APL
1) At offset 15ac48, change 02 00 56 E3 to 09 00 56 E3.
2)At offset 15ac34, 01 10 A0 E