I recently installed BIOS version F7a, however this version made my four sticks of RAM very unstable, no I installed F6 again. But now I can't get my onboard Realtek LAN to work at all, the drivers aren't able to be installed (again) and it won't show up in Device Manager (with hidden devices shown).
Another problem which might be related is that my Windows 7 (and Ubuntu Live CD and Wubi) boots are very slow.
Load Optimized BIOS -> Restart -> Install F5 BIOS -> Restart -> Load Optimized -> Restart. No luck.
Next step is to remove two RAM sticks and try out F7a and see if the LAN is working there.
And yes, the LAN cable is working with other computers.