I hope this image has made it onto the thread. If not here is a link to it.
http://clachanwood.wordpress.com/?attachment_id=818It is quite hard to see the problem on it's own so I have fitted the dodgy circle into a circular rebate I did using a post processor without arcs.
The code I used is as follows, for the defective circle.
G17
G0Z12.400
G0X0.000Y0.000S18000M3G04P15
G0X-78.000Y-0.000Z12.400
G1Z-4.650F5100.0
G3X0.000Y-78.000I78.000J-0.000F9900.0
G3X78.000Y0.000I0.000J78.000
G3X0.000Y78.000I-78.000J0.000
G3X-78.000Y-0.000I0.000J-78.000
G1Z-9.300F5100.0
G3X0.000Y-78.000I78.000J-0.000F9900.0
G3X78.000Y0.000I0.000J78.000
G3X0.000Y78.000I-78.000J0.000
G3X-78.000Y-0.000I0.000J-78.000
G1Z-13.950F5100.0
G3X0.000Y-78.000I78.000J-0.000F9900.0
G3X78.000Y0.000I0.000J78.000
G3X0.000Y78.000I-78.000J0.000
G3X-78.000Y-0.000I0.000J-78.000
G1Z-18.600F5100.0
G3X0.000Y-78.000I78.000J-0.000F9900.0
G3X78.000Y0.000I0.000J78.000
G3X0.000Y78.000I-78.000J0.000
G3X-78.000Y-0.000I0.000J-78.000
G0Z12.400
G0X0.000Y0.000
G0Z12.400
M05
G0X0.000Y0.000
M30