Hi there, I was shooting on a GL2 and looking at my footage it looks liek teh white balance is constantly shifting from warm to cool tones - I can't remember if I had it on auto white, but I believe I had it on the user-set white balance and did it my self.
I had a similar thing happen with a much different camera a few years back (a Sony DVcam, DSR200), but the results were the same, constantly shifting color temps.
In this case it started happening after the camera sustained a very light bump. It was apparently just enough to make it go screwy. Our local repair technicians were unable to nail down the problem and it ended up going back to Sony for a (unfortunately quite expensive) fix.
I tell that story just to confirm that it's not an unforeseen problem.
Don't panic yet though...
Obviously the first step would be to conduct a fairly extensive shooting test... in different environments, long takes, with absolute certainty that the camera setting are all as they should be. Maybe it was just a fluke, or you had auto white balance on and color temps were shifting enough to fool the camera into making unneccessary corrections.
If not, at least Canon's warranties are a lot better than Sony's.
I've had this hapen when shooting a Canon XL1. It occured when white balancing insude in low light. I set the white balance manually and the balance changed ok but the "White Balance Icon" still flashed slowly indicating that it did not have a solid lock on white balance (I now surmise ...(;->). I shot anyway and got the effects you described.
When the WB icon flashes like that after an attempt to manually White balance, it usually means either the object is not white OR the light illuminating it is at a Kelvin Temp lower than the camera is designed for. On the XH-A1 the limit is 2800 Kelvin.