Fixed the overheating problem! I'm not really sure why it was overheating, but it's fixed now. I drained the radiator (again) and put radiator cleaner in.
Here's a pic of me leaving my driveway on the first "real" test drive. My mission was to fill up on gas, inflate the tires and take it through the car wash.
Here's how the test drive concluded:
I got the gas, but the battery died in the line for the car wash. D'oh!
The battery is faily new. I have been putting it on a charger about once a week so it wouldn't die. I'm pretty sure it's under warranty, so I'll be taking it back to Checker. I hope it's not the alternator.