I posted this problem at another site forum and had many suggestions to look into and also noticed others with a similar problem.
This is what I found;
The main ceiling register was installed 180 degrees backwards and when it was removed during the investigation the center divider (between the return and outlet) was installed offset in the wrong direction.
This appears to have been done at the factory.
I moved the center divider over to the correct screw holes, turned the large register over this area 180 degrees and VOILA! Strong air out of ALL outlets now.
Previously I had air being blown OUT through the filter and only a trickle out of half the ceiling registers. Now return air goes IN to the filter as it should.
If you have a similar problem, take the central register down (4 screws)and study the openings from the fan and to the ducts carefully and you will probably see the problem.