We have not had similar cases reported nor do we have a known issue with Intel(R) Integrator Assistant (IIA) disabling the network interface. In view of this, and based on the tests done by you so far, before concluding the board's defective, I'd recommend the following:
1. Restart the system into BIOS by pressing <F2> during the boot process. Once in the BIOS setup utility, press <F9> to restore BIOS default settings. Reset any customized BIOS settings. Clear all DMI event logs by setting the option to "Enable", which is located in the Advanced/Event Log Configuration section of the BIOS Setup utility. Press <F10> to save the new settings and reboot the system.
2. If the problem continues, remove the LAN driver from Add/Remove Programs and ensure the NIC is uninstalled from Device Manager; restart the system and once the Operating System finishes loading all of the drivers and detects the onboard LAN controller, proceed installing the most current LAN driver (click here).