Mike Thanks for the insight, After looking back at my data I found the null value you were talking about. Not sure how that ended up there, but I deleted it out. and reloaded the shapefile ( I upload a zipped shapefile) and it seems to be working now. The error must have come about in my last upload. But anyway, that seems to have solved my problem, and like you said it wasn't something visible. Thanks again for your help Mike Thanks, Alexvalunet
... View more