When u say the starter motor is cranking, do u mean it is cranking the engine, or ticking? I've had a similar problem last night. I have a 92 32 gtst. Was driving everywhere and all was fine. Stopped at a servo, got some food, came back to start the car and the reds came on, flickered a bit then i tried to start it. No start. Just ticking from the starter. I clutch started the car and it ran fine.
The conclusion i have come to is that the starter has an internal short causing power to surge and cut out.
I'm going to put a new starter in it tomorrow and see how it goes after that. Will keep u posted. Hope that helps and good luck with ur problem.