What is your anti-virus software?

Note, 'not responding' is not the same as 'crashing'. It helps to use the correct terminology.

Apparently, I didn't have any. My IT instructed me to download Malwarbytes.

Try to start Windows in safe mode with networking enabled. - Win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode - Win8 https://support.microsoft.com/en-us/help/17076/windows-8-startup-settings-safe-mode - Win7 https://support.microsoft.com/en-us/help/17419/windows-7-advanced-startup-options-safe-mode#start-computer-safe-mode=windows-7

Still in Windows safe mode, start Thunderbird in safe mode. - https://support.mozilla.org/kb/safe-mode

Does the problem go away?

I will say that now it has been working properly for a few hours. Let me work with it for another day as is and see it the problem persists. It seems to come and go.

shamula said

I will say that now it has been working properly for a few hours. Let me work with it for another day as is and see it the problem persists. It seems to come and go.

shamula , is it still good when it is not in safe mode? And you didn't change anything - only thing you did was start in safe mode?

Could not get it into safe mode for some reason. It just seems that I need to open the program and let it sit for a while (weird) and then it operates okay. Seems to take a long time just after starting program to load messages and delete old ones. If I try to do anything during that time, the first like 20 minutes, that when it seizes up.

Then I misunderstood - I thought you had successfully gotten safe mode.

Safe mode is the first step. Perhaps you will need assistance from someone so you can do https://support.mozilla.org/en-US/questions/1145906#answer-933545