Intel support has this to say:
1) Windows 7 is not a supported Operating system for S5520SC workstation. Please refer to the URL for the list of supported operating system
2) Further, Intel X-25M solid state drive is not a validated harddisk for S5520SC workstation, please refer to the URL for the list of supported harddisk:
Does this seem like a reasonable response?
As mentioned on another thread, your problem may be worked around by plugging both NIC ports into your network.
as mentioned in another thread updating the LAN drivers will fix the problem - i had the same problem and it was fixed through updating....