You've mentioned both a DX80 and an SX80 in your question - can you let us know which one it was, as they are quite different and could cause a different set of issues depending on which one it is:
ie if it's a DX80, then you could have created a loop on the network, or if it was a SX80, then you have possibly connected an additonal DHCP server to your network which could conflict with other devices. Either way, it's unlikely that the whole switch would have gone down.
Wayne
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