Dawntreader, I have some questions for you.
1. Did you do any recent repair or servicing to your engine?
2. Did you do anything out of the ordinary to cause this?
3. What do you think is the cause of this problem?
4. Is there milkshake in your crankcase as well? Please check your dipstick.
You have a bad case here my friend. There's a damn good chance that its not just the head gasket - copious amounts of milkshake in the radiator is unheard of. I would suggest that you conduct a compression test on your engine. Do you have a compression testing gauge?
Lets wait for the Shaman to chime in as well.