Backup Exec 2012 & AVVI : "Solution is not responding" from vCenter Alert Log

Hi everybody,

I have an Vcenter 5.1B up to date, on a windows 2008 R2 up to date, one esxi 5.1 hosts up to date, the 2 virtuals machines x and y have the last vmware tools.

I receive an error on the vCenter log :

Symantec backup <virtual machine x> A general system error occurred: solution is not responding

This error occure when I start the backup jobs for 2th virtual machine y. On the vCenter log, a normal message appear after the snapshot message :

Symantec backup xx%

The two backups works fine, the snapshots are removed correctly.

Any idea ?