Eagle 6.3.0 Standard.Four layer stackup.
I have minimum trace width and clearances set to 8mil in the design rules. Some 8mil traces fail DRC width check but others (even connected to the same component) are fine.
It seems to be that any trace that connects through a via to my ground plane polygon is flagged with a width error. Nets that stay on one layer are OK. Nets that transition to another layer (but not the ground plane) through a via are OK.
The errors also go away if I change the net class to "0 default" instead of "1 power" for the ground plane
What is it about connecting to the ground plane polygon that causes a DRC error?