The current XFree86 uses Mesa 3.x. It does not support 4.x. The current XFree86 CVS is using Mesa 4.x from what I understand.
Something must be left over from when you had 4.x installed. Try re-installing XFree86.
If you compiled Chromium from source when you had 4.x installled you will have to recompile it again against Mesa 3.x.