I'm using the code below to draw a marquee with ON MOUSE doMouse.
doMouse checks which window he mouse is in and goes to FN doMarquee(mV,mH)
if it is in the main window.

Here's the issue: Everything works as expected for ~3-4 seconds, then
the cursor turns to a spinning beach ball. No bad after effects. It
continues to draw a marquee while in the beach ball state and it
reverts to an arrow on mouse up.  But why is changing?

DO
CALL GETMOUSE(mPt&)
LONG IF mH2 < mH'so marquee works backwords too
h  = mH2
h2 = mH
XELSE
h  = mH
h2 = mH2
END IF
LONG IF mV2 < mV
v  = mV2
v2 = mV
XELSE
v  = mV
v2 = mV2
END IF
CALL SETRECT(rectR,h,v,h2,v2)
CALL FRAMERECT (rectR)
flushwindowbuffer
DELAY 25
CALL FRAMERECT (rectR)
flushwindowbuffer
UNTIL FN BUTTON = _false