For the longest time I’ve been getting this error dialog when I log in:

Error activating XKB configuration.
It can happen under various circumstances:
- a bug in libxklavier library
- a bug in X server (xkbcomp, xmodmap utilities)
- X server with incompatible libxkbfile implementation

X server version data:
The X.Org Foundation

If you report this situation as a bug, please include:
- The result of xprop -root | grep XKB
- The result of gconftool-2 -R /desktop/gnome/peripherals/keyboard/kbd

Nothing bad happens (I think). Just annoying. I have the layout set to USA Macintosh and the keyboard model as MacBook/MacBook Pro. If I set it to Apple Laptop it works without the error. But- I have a MacBook Pro. Through trial and error I changed the layout to plain USA and now have no errors with MacBook/MacBook Pro selected. Yay.

For others with similar issues- this thread may be enlightening.