Mate to Axis Error?

I having trouble with a operation in Solidworks 2008 SP3.1that seemed to work without issue in 2006.

I am working with cambers, fabricated steel I-beams. The top flangeof the beam is a single line sheetmetal part based on a 6018 inchradius arc. Standard profile junior I crossmembers are circularpatterned along the length of the arc. The center plane of thejunior-I section is mated to an axis generated off the top surfaceof the upper flange. To space the upper surface of junior-Icrossmembers down 1 1/4" from the top of the beam flange, I used adistance mate (6016.75") between the axis and top surface of thejunior I. When I measure the distance from the top of the junior-Ito the axis it is 6016.8125.

Is this a bug in Solidworks or is my procedure flawed.SolidworksEdrawings