Sorry for the trouble you are having.
There are 2 possibilities. The anti-malware you are using on your computer is blocking ClassicStartMenu.exe or interfering with its behavior. Look in the settings of your anti-virus to whitelist C:\Program Files\Classic Shell\ClassicStartMenu.exe as a safe process, which tells it to exclude/not to scan it.
Another possibility is (and from your description it sounds like that) for some reason, opening Classic Start Menu settings is causing your Explorer.exe to crash.
If Settings still don't open and Explorer is crashing, you can capture a crash dump using the process described here:
viewtopic.php?f=12&t=6 . Run procdump -e explorer.exe and then try to open Start Menu Settings which will crash Explorer. Upload the dump file here.