help:host（xenserver）in Alert state,and i can't do any

[sunko2014]

hi:
   Because power off, the host（XS6.1） was forced to restart, when resumed,
in Cloudstack portal ,the host has been in a alert state, can't be deleted
from portal and can not reconnect, vms in this host can't control, how to
deal with this situation?
   environment: CS4.1.2+CS6.1