MOTION 3 stuck in playback loop

Looping playback either with or without a RAM preview won't 'whoa!' when I say 'whoa!' - or hit the spacebar or click the 'pause' button, either once, twice, or man many many times.

Loop just keeps on playing, effectively locking me out (until RAM takes a breather?).

Won't stop. Might as well have done all this graphic work in FCP and waited for the endless renders; would have taken as long (or less?)

What to do?

rav