James,

As with any CMM radius'have always been a problem. Any radius with less than 60 deg. of arc will cause a reporting nightmare.
But there are some things you can try:

1)Enable the partial arc algorithm under the GEOMeasure customization setting.
2)Increase the number of points. And I mean really increase them. Take as many as possible. The more the better.
3)Use the auto-measure function in the circle feature and set the start and end angle to encompass the radius. You will create much better vectoring then if you probed this manually.
If possible use the scan option and select a small pitch and scan around the radius. Use DMIS construct (or use the SCANMeasure option, if you have purchased this option) and build the radius from the scan. I have included some examples under TIPS in this forum. If you are not familiar with setting up a scan e-mail me and I would be happy to help you do that.