My low coolant light started blinking while I'm driving. I checked to make sure there was ample coolant, and the fuild level was fine. The engine is running as cool as it ever was. Any ideas why this is happening?

Also, due to a recent dead battery, my Theft Lock on my radio locked me out. I guess the prior owner had initiated the feature and never left the code (I bought the car used from a dealer). I tried to take a few guesses to unlock it and now I'm getting the "INOP" light and the radio has locked me out permanently. Anyone know how to clear/unlock the radio so it works again? Please drop me a line at egumban@yahoo.com. Any help would be appreciated!!!