Check your coolant temp sensor. These sensors frequently cause the "won't re-start when warm" problem.

The sensor's tend to die "cold." When the engine's cold, the sensor reports "cold engine" to the ECU and the ECU sets up the injectors to start a cold engine. As the engine warms up, the sensor reports this to the ECU, and the ECU leans out the mixture accordingly. So far, so good.

But then, the sensor dies and "goes cold" on us -- ie., it tells the ECU that the engine is now cold. You can continue driving and you'll never notice the difference, cuz the O2 sensor has command now, and it tells the ECU to lean out the mixture. But when you stop the engine, and try to re-start it, the sensor is still telling the ECU that the engine's cold. So the ECU starts dumping fuel into the combustion chamber and floods the engine.

Wait a few minutes for the engine to cool down, and it'll start right up. If this sounds like what's happening to your car, check that sensor.