Swept Flange on a curved profile?

Trying to create a swept flange on a curved path and can't seem to get SolidWorks to do it. I've tryed a simple line profile on a half circle path with the same error message. Any one have any idea why I can't sweep a profile along a curved path? Error message is, "The profile does not intersect the edge on which the flange is to be created." I can use the swept flange feature on a rectangular path with no problems. Any advice would be great. . . screen shot is attached.

SolidworksSheet Metal