I have the exact same problem with my DX58SO. After sleep, the network adapter reports "cable disconnected" and if I disable/reenable it disappears from the list of adapters in "Control Panel\Network and Internet\Network Connections". After rebooting all works fine again.
OS: Windows 7 Ultimate 64 bit
I believe this question is about the same problem: http://communities.intel.com/message/93877#93877
Here is a copy of the email I got from Intel Technical Support. I actually fixed the problem before I got the email. Downgrading the bios fixed the problem for me.
Thank you for contacting Intel Customer Support.
I understand the LAN adapter turns off after the system comes back from sleep mode on Windows 7*.
In this case, we will recommend you testing the system with BIOS version 5200. Please perform a BIOS recovery to do the update. The file can be found at: http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=18938&ProdId=3018&lang=eng
For BIOS recovery instructions, please refer to: http://www.intel.com/support/motherboards/desktop/sb/CS-023360.htm
If the issue persists after using BIOS version 5200, please try using the LAN driver version 14.6. You can find this driver at:
Message was edited by: Apota