Colgate,
We wish we knew for certain. Details are scant to say the least.
To clarify a few points for you:
1) Jetgreen were not an airline, but a tour operator. Icelandair provided the aircraft etc. I am not well up on Aviation regulatory law, so I am unsure exactly what the legal differences are in relation to capital etc.
2) Jetgreen had not secured Dublin airport slots for new routes to Rome, Faro, Nice. Aer Rianta (Dublin airport owners) ordered them to apply for said slots at once, or face refferal to the aviation regulator here in Ireland. It is to be assumed that this had something to do with it's downfall. One theory is that investors pulled the plug once they heard of this.
3) There was also an incident before Jetgreen even got in the air, where they publicly stated that Icelandair would provide the planes. Icelandair were not too happy as this had not been fully agreed upon (though obviously negotiations were advanced)
Jetgreen should have learned a lesson from this, but clearly didnt.
I'm afraid that is all we really know for sure, but we wait for further developments, and with a hope that this is not allowed to happen again.