New switch never plugged into any network or ever been configured, just updated IOS and I get same message.Mine is on a WS-C3750X-24T-S running 15.2(3)E1 (C3750E-UNIVERSALK9-M) c3750e-universalk9-mz.152-3.E1.bin.Brian 

https://tools.cisco.com/bugsearch/bug/CSCug68370 WS-X4908-10G-RJ45 and Broadcom 57810S 10Gb BASE-T interoperability issueCSCug68370DescriptionSymptom:10Gbps BaseT ports (on WS-X4908-10G-RJ45) connected to Dell 820 servers with Broadcom 57810S DP 10Gb...

Thanks Shane for the quick update to my posting...  I just noticed in the documentation for 15.0(2) SG8 IOS  that the "WS-X4908-10G-RJ45" is not on the supported hardware list, or mentioned anywhere in the documentation for Caveats Resolved or Open. ...

I just upgraded to 15.1.2 SG2 that was released in Sept 2013 and am having this same issue with upgrade from 12.2.54.  Took 2 of my ESX ports on the WS-X4908-10G-RJ45 a range of 11 min and 28 min to come up.  I applied the commands to set the 10G to ...