You need to alter your XF86Config. What you need to do is look what the identifier is in your screen section
Identifier "Screen Configured"
Say it looks like the above change the serverlayout to match it like
Identifier "XFree86 Configured"
# Screen "XFree86"
Screen "Screen Configured"
I've commented the line out with a hash, You can simply edit or delete it if you prefer.