Try extruding a bit first - maybe 20 on Cura before retracting or trying to remove the filament. I talked to a Lulzbot Tech yesterday about this problem with ABS (I went to extrude a bit then retract and had the filament stick and would not go either direction) - was able to remove the filament by pulling hard by hand.
He did suggest covering the fan intake and fins with something to warm up the area a bit if things got stuck before taking things apart. Another Tech suggested a few months back suggested the same thing and I think the suffested time was around 10 to 15 minutes.
He said that my extruding then retracting was the suggested method.