Re: Wasn't there a TSB on '07 WK airbag??
Many times, this is caused by the wiring under the drivers seat. If the seat is moved often, or if stuff gets tucked up under there the wires for the weight sensor can suffer from a poor connection.
You can check these connections to see if that could be your problem (there are certainly other things it could be, but this is a quick, easy, cheap thing to check yourself).