This was a known issue in a previous version of Chimera that came from the Chameleon trunk that I removed in later versions of Chimera. It would write the boot flags to nvram.
To fix you need to run the following commands in Terminal:
nvram -p (in the output look for a variable I think called boot-args or something similar. it will have -x as a parameter)
nvram -d boot-ags (or whatever the name was from the previous command)
Then make sure you update to the latest Chimera so this doesn't happen again.