Do you want to control using STP on these 2 links ? You can create the priority of the link such that 1 link is always blocking and other frwd. Otherwise you can try using flexlinks. STP cannot coexsit with flexlink.http://www.cisco.com/c/en/us/td/d...
Either you need a L3 device in b/w these 2 VLAN or you can explore belowhttp://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/CLIConfigurationGuide/PrivateVLANs.html
How did you format the USB. May be format the USB in working 903 and try on the non working. else USB slot may have gone bad..From rommon you can verify following as well;dev - will list usbdir usb0:thanks,
