yeah rx7, you really ought to give us more info next time.. i fixed some so we'll all know what year your truck is. lol
and yeah, there is a switch in the ATs that won't let it start in any gear. it should start in N w/o problem though. next few times just move your shifter to N and then try it.. if it fires most of the time then that switch is the cuplrit. i said most because sometimes even in N that switch could be active. gently! move the shifter around, just little, w/o going out of N.. if it fires after you tweaked it then see 3rd sentence back.
the wiring diagram clearly shows the inhibitor switch in proximity to the shifter (below the black arrow in the upper right corner) and i bet that if any of this is actually the cause then it's the switch itself and not the relay. the switch is way more prone to wearing out.