engine cutting out Options

[soma]

Alright, so last night about halfway through my trip to go home, I pull up to a stop light. When I take off in first, the engine stalls (like it would if I had let clutch out w/out giving enough gas... but this was not the case). I start it back up and continue on my way... I pull up to another light, push the clutch in, and the engine dies.
Now it starts back up just fine if I give it a little bit of gas, but the second I push the clutch in again or let the rpms get below 1000, it cuts out.

Note: it does need a new thermostat.. it has been running ENTIRELY too cold lately. I'm not sure if that could be part of the problem.

I stopped at a BP and got some gas on my way home before all of this happened.. does anyone think it could've just been poor quality gas? Should I change the gas out and clean the fuel filter?

..Anyone had this problem before? I miss driving it already Help!