Immobiliser maybe ? - mine played silly whatsits last week when I did some work at the VW HQ in Milton Keynes, parked in the visitors car park, worked for 3 hours, came back and it would spin over but not fire. Locked and unlocked it (using the button on the key) several times, and it eventually fired............not had any problems since :?
The whirring sound - does it sound like a little fan running ?, and is the noise coming from by the headlamp level adjust knob ?, if so it's the air-sampling fan for the climate control. TUrn the A/C off and the noise should stop.