Slow throughput on teamed NIC's

Hello,

I have Backup Exec Small Business 2012 installed on my new media Server SBS2011.

The server has 4x 1 GB NIC on one Teaming Load Balanced.

When I backup a client (Win7 x64 with SSD) it seamed the media-server works on half duplex.

The load is 50 % on NIC2 on reading and about 50 % on NIC 3 with writing to NAS.

But when I copy a big file with windows explorer form \\client\C$ to \\NAS it runs with 99% on reading and writing.

Is it a configuration problem?

Thanks for any help.