After a CIS update on the 21.1.10 to VDB 3656 all my XP machines locked up shortly after booting followed by explorer.exe crashing. Win 7 machines were unaffected. Tracked problem to program tsmuxergui.exe which had a shortcut in the quicklaunch bar. As soon as the system attempts to access the file the system freezes. No alerts are generated by CIS and a complete lockup results. I suspected the update and uninstalled CIS in safe mode and problem resolved itself.
Here is a workaround: Boot into safemode and delete tsmuxergui.exe and shortcuts. Disable Defense + and reinstall tsmuxergui.exe. Add tsmuxergui.exe to safe and trusted files, reenable Defense +.
Cheers