This is my first post on this forum, hope you can help me

I have recently purchased your product Veeam Backup & Replication 4.1.
My enviroment has 3 servers, 2 of them in a cluster using Vmware vSphere 4 U1 Advanced.
On my enviromment I amd running 17 Vms (DC,Exchange 2007, SQL Server 2008, ISA Server 2006,...).
I installed your product on a VM inside my cluster and I am using Virtual Appliance mode to make the backups. Everything so far so good.
My problem came when I tried to backup my SQL Server 2008 using your VSS. I cannot backup this server. It always gives me VSSFreezer: Failed to freeze guest, wait timeout error. It does not say how many miliseconds is the timeout.
I have read many threads on your forums regarding this and I´ve tried so far everything: Disabled Vmware VSS Quiescence, create registry DWORD VSSPreparationTimeout,...
On the Vm, it seems that VSS is working fine because it doesn´t show me any errors on application / system events, vss services (veeam vss, microsoft vss,...) start correctly and it shows me that backups of my databases where made OK.
I was thinking that maybe the problem is regarding my vCenter being part of the cluster and using the SQL Server as its DB. Maybe when I launch the SQL backup, vCenter losts connection to SQL, Veeam goes mad not finding vCenter server and backup fails.
Any ideas? Could you help me please?
Thank you so much!
Bye