Hello,
The problem is likely to be fixed.
The backup seems to be working now, so I'll describe below what has worked for me:
First of all , I realized that the 2 Remote agents installed on my 2 clusters nodes were not up to date.
For some reason the remote installation from the Backup Exec Media Server was not working, so I had to install it locally on the 2 nodes using the Backup Exec 2010 DVD we had.
The problem is that the Remote Agent I was installing from the DVD was not the same version as the one available on the Backup Exec Media server, which I could not deploy from the network.
I had to manually copy the Remote Agent from the Backup Exec Media server using the following procedure:
http://www.symantec.com/business/support/index?page=content&id=TECH158716
And then install this version on the 2 clusters nodes. Once it was done the backup was still not working, but I had other error messages. I also had to disable the antivirus on the 2 nodes to make it run . I already did that with the old remote agents but it was still not working. I will find a way to set up the antivirus not to make the backup fail.
Thanks