vmkernel listed as disabled

Hi,

I am in a situation where vmk1 on my esxi4.1 host is somehow disabled. The enabled column in esxcfg-vmknic -l says "false"...

# esxcfg-vmknic  -l                             
Interface  Port Group/DVPort   IP Family IP  Address Netmask           Broadcast    MAC  Address      MTU     TSO MSS    Enabled  Type

vmk0       289                        IPv4         10.65.xx.xx  255.255.224.0  10.65.xx.xx    xx:xx:xx:xx:xx:xx  1500    65535          true         STATIC

vmk1       511                         IPv4         10.65.xx.xx  255.255.224.0  10.65.xx.xx    xx:xx:xx:xx:xx:xx  1500    0                 false        STATIC

It's also gone from the vCentre GUI. I tried various forms of esxcfg-vmknic -e but i'm not clear on the syntax and get the message "invalid port group".

How do I enable it again?

Thanks

Nick