Failed to migrate vm's from ESXi 5.0 host to 5.5 host .

Hi,

I have upgraded vcenter/ vsphere from 5.0 to 5.5.

With vcenter upgrade i have no problems, everything went smooth. The problem is in the hosts. I have upgraded 3 hosts from 5.0 to 5.5 without problems, but I can't migrate vm's from an host with 5.0 to an host with 5.5.

I receive the following:

"... 
  The vMotion migrations failed because the ESX hosts were not able to connect over the vMotion network. Check the vMotion network settings and physical network configuration.
  vMotion migration [-1062728319:1381258372348912] failed to create a connection with remote host <192.168.13.135>: The ESX hosts failed to connect over the VMotion network
  Migration [-1062728319:1381258372348912] failed to connect to remote host <192.168.13.135> from host <192.168.13.129>: Timeout
  The vMotion failed because the destination host did not receive data from the source host on the vMotion network. Please check your vMotion network settings and physical network configuration and ensure they are correct.
..."

The migration works without problems between hosts with the same version.

Any ideas?

Thanks

Carlos Baptista