Originally Posted by CBelli

did you sparge over 170 degrees?
high sparge temps can cause exactly what you are describing...

one other idea.... does the taste go away if you let the beer sit in the glass for 10 min?

this is a complete shot in the dark but I once had an over carbed pale ale that had a very bitter aftertaste and believe it or not I decarbed it and the beer got much much better...