help!! engine failsafe prog.....engine acting weird!

[vskchoi]

hi all
this is what happens today, it is -25 outside, my gas tank is just a little less than half full....the car was stopped outside for 1 hr after a 30 mins drive.
when i came out, started the car, the idle needle is jumping...acting as if it will stall anytime...then i press the gas keeping the rpm up above 2000...when ever i release the gas, the car stalls....and so i left it like that for about 5 mins....until the idle stays around 1000....then i drove for couple mins...and all of a sudden it stall, and "engine failsafe prog" was on...and the check engine light was on....started it again, then stall again, went like that for a few times, then finally got it started and seems normal again.....went home, fill up the tank, everthing seems normal at this point, but the check engine light is still on...any idea whats the problem? could the gas tank be frozen becasue of less than half full??
thanks alll!!!