SOLUTION......at least for me
Applied the vcredist_x64.exe = 64-bit patch as per the "IMPORTANT: Fix MWLL Launching Incorrectly" post
(sticky top of Known Issues Forum).
This corrected the "disconnected from server" error (...."cause=1; msg='Malformed packet' ")
Not sure if it is relevent but....prior to the above fix patch, the loaded MWLL Wars Menu did not list 4.3 on the bottom right of the Menu screen (showed 1.xxxx?).
After the patch, it lists the correct MWLL 4.3 version number.