Guys ..need help.

Got an intermittent spanning Tree problem i cant seem to be able to trace.

Keep seeing errors of Duplicate Mac address via HSRP interfaces on only two vlans.

Scenario :

Two Cisco 7609 in HSRP pair, down stream trunks to Nokia ESB Switches ( intregrated into Media GWs ) .

Problem only stops when you disallow the vlan traffic from the trunk port connecting the two 7609s.

Can anyone give a quick heads up on how to locate this ?