More than likely your water pump is beginning to fail. Just happened to me. Same exact symptoms, even the power loss between gears. Mine would give me the overheating CEL after driving it for more than 20 mins. If I drove less than that it wouldn't give me the warning light.
Replaced the pump and thermostat and back to normal.
Here's a thread that may help
http://www.1addicts.com/forums/showthread.php?t=798195