Opening Notepad in a shell creates screen defects or freezes QB

In screen 12, the file opens, but QB is minimized to the taskbar and is frozen. The screen displays a colored tiling effect. I have to close it by force.

So I tried Screen 0 and get a blue mouse cursor block on the screen when a maximized window. Minimized window works fine.

SCREEN 0: WIDTH 80, 50
CLS
filename$ = "tst2.txt"
SHELL "cmd /c start notepad " + filename$
PRINT "END"

SYSTEM

Any thoughts? Thanks!

Ted