If I understand your post correctly, Experian is showing March 05, April 05 and May 05 late payments, and you filed your BK in Oct 05?? Any late payments before you filed your BK are fair to report (if you were indeed late).
I'm not sure what you are saying when you say "now for 2006 they are showing key derog for June"?? Can you explain??
If this is a debt which was discharged in BK, you need to dispute it with the CRA. Dispute it as "this account included in BK".
The only way they would be allowed to report a late payment would be if you had re-affirmed the debt, or it was a secured debt (auto loan for a vehicle you kept for example).