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 E3 to 00 10 A0 E3
Above two steps took care of safe mode hack.
3)Per Enrico59 post to bypass nag screen in 5.1 firmware
At offset BE9A4 ,change 05 00 00 0A to 00 00 A0 E1
All the credit goes to Pionara for identifying which hex code has to be modified .
All I did was identifying the offsets in the new navi.exe to make the hex code change
Happy Holidays!