Whirlpool QuietPartner II Dishwasher will not drain on normal cycle?

[super20g]

I have a Whirlpool QuietPartner II Imperial Series Model DUL200PKB1 that will not drain.

Inside the dishwasher I took the bottom apart and cleaned everything, sucking out the drain as well.

I also removed the hose from the disposal and sucked that out as well with a wet/dry vac to ensure there were no blockages.

After reinstalling everything, the dishwasher would still not drain.  I then hit the Cancel/Drain button and it drained!  

After that I ran a rinse only cycle and it drained completely.  I ran the Normal wash again and it did not drain.  I ran the heavy wash cycle and it drained as well...  

Why would the normal cycle not drain but all others do?

Thanks for your time and help.

Model Number: DUL200PKB1