Sorry for the late reply.
We had the alignment performed by a dealer. OK.
2 trips later it was out even further.
My regular mechanic, who doesn't align, suggested a specialist.
The specialist aligned Sept. 2012. Have taken 5 trips since (~2500 miles total) without a problem.
Spoke with a former Nissan dealer. He indicated that the rear end is somewhat tricky, in that if a specific part set is not put together right it can `easily' come apart, resulting in misalignment. However, once aligned there really shouldn't be a problem.
Bottom line, the dealer probably doesn't know how to align.
Fingers still crossed.
Mark and Sharlene