Thank you for the response.
The system is a Supermicro X8ST3 2.0
The OS is Windows 7 Professional SP1. All updates are installed.
Let me explain the history.
The system was installed in de past with de OEM driver Intel_PRO_v16.5 by someone before me.
Then I downloaded Intel_PRO_v19.5 from Intel and updated the network driver.
After that the problem ocurred.
So I complitly removed the driver and reïnstallled Intel_PRO_v19.5
But the problem consists.
So I thought to solve the problem by removing the driver again an reïnstall the Original one Intel_PRO_v16.5.
But that did not solve the problem.
Thank you for the information and clarification. Please try to use the driver available for Supermicro* specifically for your system
http://www.supermicro.com/support/resources/results.cfm(Please note this is a third party website Intel has no control over the content of this site).
Hope this helps.