My mother has been experiencing a severe issue on her computer for several months. After I got her a more performant motherboard today, the issue seems to have worsened rather than improved. I can't find any useful information to debug this problem, so I'm hoping someone else might have an idea about what is going on with her machine.

The issue only seems to affect software from Mozilla, namely Firefox and Thunderbird. After a few minutes of uptime, either Firefox or Thunderbird (usually the first) will crash, bringing up a popup that asks whether I wish to submit a crash report to Mozilla. Once a crash has occurred, the affected program will no longer start up until the computer is rebooted: The crash will now occur immediately as you try running the application. I've verified that no older process copies of the program are still running, tried a fresh profile and running in safe mode, and even logging out and back doesn't fix it!

When running FF or TB from a console once they become affected by the crash, I only see the following lines before I get the crash popup:

ExceptionHandler::GenerateDump cloned child 2855
ExceptionHandler::SendContinueSignalToChild sent continue signal to child
ExceptionHandler::WaitForContinueSignal waiting for continue signal...
Does anyone have an idea of what might be happening? Why would Firefox / Thunderbird periodically crash for no reason, and most importantly what does it change in that session that causes them to no longer start up until the computer is rebooted?