Can someone identify these wierd marks I get while rendering

Hi, im new to the forums, and have been playing with blender, attemoting to make games for a while. However ive decided to give rendering a go.

I’ve started to render a Volkswagon MK1 Golf, and i’m getting these weird random blotches, around where I have mirrored the object.

http://img685.imageshack.us/img685/6448/golfrenderproblem.png

Any ideas what I’m doing wrong?

They appear to be on the centre line of your model. If you are using a mirror modifier check you have ‘Clipping’ selected and you have no vertices crossing the mirrored axis. The Mirror modifier should be above any Subdivision Surface modifier you have in the modifier stack.

apply a CTRL + N to correct normals, you have scaled by -1 in one of the axis to invert part of the car, and you are seeing the seem. Be sure to remove doubles and check normals.