This is incorrect. I took my ATP written in March of 2008. This was prior to getting hired at Pinnacle because it was required for the interview. I quit Pinnacle in December to fly single pilot in a Citation Mustang. I did my training at Flight Safety and it was determined that I did not need to retake my written. Reason was because I was currently employed by a Part 135 company and was in their PIC training.

Read the regulation that was already posted in this thread. No where does it say that you had to be employed when taking the written. It doesn't even say that you can't leave one company for another. You only have to be "employed as a flight crewmember by a certificate holder under part 121, 125, or 135 of this chapter at the time of the practical test."