SQL Server 2008 R2 – Fast Local Backup, Very Slow Backup via Network

Since last week, i'm having this problem.

Backups are taking forever to be done if I make them via Network.

If I backup the database to a local disk ( or N'nul' ) it's very fast.

It's strange because even with my personal PC I can't make network backups ( there's nothing with the cluster, or configuration that we have in the production instances ).

In This connect item they say something about a SQL 2005 issue.

What can we track to find the issue? What perfmon counter can we use?

We have already restarded the servers. Restarted instances. restarted clusters. Disabled Anti-virus. Nothing helped us.

This is some logs:

Via NUL:

backup database My_DB to
disk =N'nul'
–Processed 542896 pages for database 'My_DB ', file
'My_DB ' on file 1.

–Processed 382456 pages for database 'My_DB ', file
'My_DB ' on file 1.

–Processed 1 pages for database 'My_DB ', file
'My_DB ' on file 1.

–BACKUP DATABASE successfully processed 925353 pages in 19.911 seconds (
363.081 MB/sec).

Via Network:

backup database My_DB to
disk ='\Server\D\BACKUPS_TEST\teste.My_DB .bkp'

–Processed 542896 pages for database 'My_DB ', file
'My_DB ' on file 1.

–Processed 382456 pages for database 'My_DB ', file
'My_DB ' on file 1.

–Processed 1 pages for database 'My_DB ', file
'My_DB ' on file 1.

–BACKUP DATABASE successfully processed 925353 pages in 129.223 seconds
(15.944 MB/sec).

I can copy files through servers with no problems. I really have no Idea what to do. I would be grateful to share more information.

EDIT1:

Something I notice is this query below ( in the destination server ):

WAITFOR (RECEIVE message_body FROM WMIEventProviderNotificationQueue),    TIMEOUT 5000

There are a lot of websites saying different things about it, so, I don't know for sure what it is.

I can see this query running via trace or with sp_whoisactive. It runs, then it restarts itself. Could this be the problem ??