Wall Reference Line is offset 1/2" on all walls when it's Outside or Inside Face

[architect]

Here are some screenshots illustrating the problem:

[Lee Hankins]

You need to change the active edge offset to 0. Look in the info palette at the top worth the wall selected or open the wall preferences and you will see it there. 

[Jp1138]

As Lee says, maybe you have entered a displacement to the reference line: