You could be my wife with the amount of patience you display. Waiting an entire 25 minutes must have been a "pins and needles" situation for you.
The other thing you might want to do is update your user CP, link found at the top left corner of any forum page, to reflect your location so any other member who is local to you can rush to your aid immediately upon you posting a problem.
"What is it?" Obviously you are either low on coolant, probably, or your coolant has a very low boiling point and during your "little hard driving" experience the car overheated. If you are using G12 mixed to the correct proportion then I would assume the former and doubt the latter.
Replacing the G12 in the correct ratio mixture will correct the problem if, and only if, your level of coolant was only low to begin with. If it were me I would determine if the cooling system has a leak before topping off and possibly wasting expensive G12. Fill the system with plain distilled water to the proper level, run (drive it normally) it a while and check the coolant level while still hot and again cold. If low then determine where the leak is and remedy with the appropriate repair and then invest in the G12.
Good luck and be a little more patient.