You need to disable spanning tree on that port.  Here are the commands: console> enable console# config console (config)# interface ethernet g1 console(config-if)# spanning-tree disable  
I have a Powerconnect 5324 to which I've connected a Supermicro motherboard with an ipmi (lights out) running on its first interface.  If this doesn't ring immediate bells, this is an on board networked device that runs on the same interface of the motherboard but at a different MAC.  This device remains active even when the machine is off (as long as it has power) and gives access to the console, allows you to manage the power states of the machine, etc.   The problem is that, when connected to the Powerconnect 5324 and the machine is power cycled or powered off the ipmi is unavailable (does not respond to pings) for anywhere between 10 to 30 seconds, missing any opportunity to access bios, etc.  This does not happen on unmanaged switches (ie Netgear GS108), where the ipmi may drop for up to a second or more, maximum.  I'm not sure where this could be hung up so, to be sure there isn't an old configuration I've left that may be interfering with the performance, I reset the Powerconnect 5324 by wiping the flash and restarting.  This has not resolved the problem so I don't think this is as much a configuration problem as the lack of one. Can I get some help on what may be causing this latency on configuring this port to allow access to the ipmi?  Shooting in the dark, but is there a configuration required, for example, for a port that connects to an interface with two devices/MAC?      
Configuring for ipmi (lights out) servers on Powerconnect 5324