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Spanningtree and port channels

I have two 6509's in my distribution layer and nine 6509's in my access layer.If I set up dot1q trunks in the on mode from my access to distribution layer spanningtree blocks at the access layer,GREAT!

Now,when I form two port channels(4 dot1q trunks in each) from each access switch to each distribution switch,the Spanningtree blocks at the distribution layer. There is no connection between the distribution switches. There is however excess traffic now on one of the access switches(BPDU's).All media is fiber.

Why does the blocking occur at distribution layer after forming the port channel? Any help greatly appreciated!!

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