It appears that you are hitting a known BUG (for nxge 6843221, for bge 6963866).
For nxge NIC's:
When 'dladm show-link' is run (for example by explorer) it will attempt gather information about the status of all network interfaces in the system. For nxge interfaces this results in us calling nxge_check_mii_link via a taskq if the link is not plumbed.
This then in turn calls nxge_link_is_down which is responsible for producing the following 'notice' message:
May 20 09:51:44 v4v-t5440b-gmp03 nxge: [ID 339653 kern.notice] NOTICE: nxge2: xcvr addr:0x1b - link is down
For bge NIC's:
When 'dladm show-link' is run it will attempt gather information about the status of all network interfaces in the system. In the case of bge interfaces, if an interface is unplumbed/unplugged, it willgenerate the following
Jun 24 08:50:34 t1000 bge: [ID 801725 kern.info] NOTICE: bge1: link down (initialized)