Sorry to hear you are having this problem. when it won't start try jumpering the dme relay. as you plug in the jumper listen for fuel running in the fuel rail to confirm fuel pump. now try to start it . if it won't start then check for spark by removing #1 wire, plug in an extra spark plug, with a aligator lead from the spark plug threads to ground, and then crank and observe if here is blue/white spark. remove the dme jumper afterwards so as to not leave the fuel pump running.
if there is spark this means the dme is probably ok however there have been cases where there is spark but no injector pulse due to a dme problem.
edit: constant +12V is normal on the injectors, the dme will provide the negative 12V when it pulses the injector.
The dme jumper is simply a 3-way Y connection from pin 87 (12v power) to 87b (fuel pump) and pin 30 (dme power)
More info on the Dme relay and jumper here:
http://www.clarks-garage.com/shop-manual/fuel-05.htm