Let me ask the group a theoretical question...
I am not suggesting this is Gunguy's problem, but...
If you had a substance (like some type of oil) in the keg when you racked your beer into it, would the co2, still be absorbed into the beer?
I experienced something like this a couple years ago... I had a portable co2 charger that connects to a 2 liter bottle with a carbonator cap. The only co2 I had handy was from an air gun, so I used it... A short time later I noticed a oily film on top of the beer. Checking a bit closer, I could smell the oil from the co2 cartridge (I think it may actually serve as a lubricant for air guns). I know carbonating in a 2 liter is far from ideal, but was just curious how it would go... bottom line, it didn't. There was plenty of pressure (the bottle got very tight). I left this in the fridge for 3 or 4 weeks, and resulted in zero carbonation.
I wonder if the oil created a barrier that prevented the absorption of co2. And I wonder if any other common substance may have a similar result?