I am working on a project, and there is an embedded system inside a metal housing. The unit can be turned on at ambient temperature running application software or test software and then is put inside a temperature controlled environment down to -45 degrees celsius. The system is allowed to stay at -45 C, but internal housing is probably at a slightly higher temperature with all of the circuitry being powered. While at -45C, the system begins to hang, and then the watchdog resets it. When it reboots, it fails to boot. This has happened on multiple units. When the systems are taken out of -45C and JTAGed they repeatedly show the exact same memory location in the NOR Flash having the exact same wrong value, and this location is in the boot image section, which would explain why it doesn't boot, but doesn't explain the hang necessarily because the units are operating off of the image after it has been sent to RAM in the beginning. This part is very confusing, because it leads the error to seem not random at all (what are the odds of the exact same memory location having the exact same wrong value at each failure?). Also the NOR Flash has built-in lock protection, so that when it resets the boot image should not be corrupted. This system has been out in the field, and this problem has only been noticed since a different PCB manufacturer was used, so the manufacturing process has changed; however, the layout has remained unchanged, and the boards have been examined to see if there has been any noticeable change without finding anything. The limiting operating temp spec on the internal components is -40, so the unit is being used outside of its limits, but this still does not explain why this didn't happen before PCBs were changed and why this specific, nonrandom, failure occurs. Has anyone had an experience like this or have any helpful ideas what could be the problem?