You're not showing enough information in your screenshot. Provide a new image of the Fog window with the Preview off, turn on Show Points, and Select All so we can see the handles. Chances are it's related to either a stray point, or an unclosed path, or weird start point or something. Also, you might get better responses to a technical issue like this by posting in the Build forum. (But don't post twice -- maybe a moderator can move it for you.)

It looks like it has been sorted, I think it may have been a case of the 'weird start point' you mentioned. Thanks for your help mate!