Whine from my keg

I recently bought a 4 keg lot (ball lock) from an online retailer and have had no problems with any of the kegs until now. I recieved 1 "ugly duckling" keg that is different from the rest. It has a 12 point liquid out post on it and a diptube that curves near the end with the tip sitting in the center of the keg. (I dont have it in front of me, so Im not sure who made it) The keg has been hooked up to CO2 for a few days to carb up a wheat for a BBQ on Saturday, no leaks, everythign seems fine. However, when I try to pull a pint, I hear a whining noise coming from the keg. The flow on the keg is severly reduced and it spits almost all foam. I am inclined to think that there is either a blockage on the dip tube, or that the tube is crimped somewhere. Anyone else ever experienced this? Im planning on taking it apart to see whats going on tomorrow...

Is this the only keg it does it on? You have multiple kegs hooked up? Could be your co2 tank whining. If you have multiples hooked up and only one tap does this, you're sucking air in somewhere.

I'll bet the beer in that particular keg is so good your keg is crying each time you take a little more beer away from it