Configured rule include inspections, rpf, and other firewall security function (like accelerated security path).

http://www.cisco.com/en/US/docs/security/asa/asa80/command/reference/s2.html#wp1351326

It will be good to look at the overall steps the traffic flow took, and from there, kind of determine, which step previous or  next, that may have contributed to the packet being deny.

You may have configured acl to allow source to a destination, but then, the flow may take a different path, due to a misconfigured/conflicted NAT, and result in the deny of the flow.

Regards,