[greyguy]

I have had the same problem as you but it has affected my 6 iron also. The interesting thing is that I can strike my 3,4, and 5 more solidly than my 6. However the 3,4,and 5 are hybrid clubs which I know are easier to hit. I maybe be going to a 6 hybrid if I can't get it straightened out.
My typical 6 iron shot using a hitting motion is a lower trajectory (like a 3 or 4 iron) which tends to hook left and short.