PC reboot, could it be one of the QMutex undefined behaviour ?

[yellowmat]

The program is currently in use on a debug PC with another SYSTEM without any bug ... as the PC and SYSTEM are diffent, it is not possible to say that one or the other is the source of the problem.

In fact my program run on an embedded PC since a few month without any bug. My problem is that I made some changes on the source code of the program a few weeks ago (using QMutex to protect my HMI object access), something very trivial I think, so trivial that I am (quite ) sure that is not my fault. In my opinion, the source of the problem does not come from my program but I prefer being sure before lookin for the other possible sources I am thinking of.

[high_flyer]

I could not quite aunderstand if the "new" version of your program, the one with the changes you inserted with the mutex, runs on both systems, or is it that the version with the changes only runs on one system.
You should try to run the "problematic" version on more than one system and see how it behaves.
If it only has problem on one system/configuration then it is more likely the problem is the system (but ofcourse, not 100%), but if the problem is the same on other systems as well, then it is likely that the porblem is your program.
NEVER asume that threads are trivial!!
Small changes in mulithreaded programs can introduce "hidden" problems very easely.