This is my first question post for this community and this may seem like a stupid question.  I have a power connect 5448 which is brand new to the network.  The switch seems to be fine but i connect it into the network, which uses Cisco core switches using compatible fiber GBIC the entire network comes down including internet access.  I have other powerconnect 5448 swicthes on the network that have no problems whatsoever.  The only thing using the switch is vmware servers (which have all networking on a seperate subnet from the rest of the network) along with virtual sans on the servers.  I am pretty close to 100% sure that the servers are not causing the issue.  Is there any reason why this swicth would be having problems with the cisco core switches.  Is the default IP address of the swicth possibly causing an ip conflict with the core switch?

Thank you for any help you can offer.