OptiPlex 9010 - LAN adapter and BIOS updat problems

Hi,

I couln't say exactly from when, but recently I have a problem with my OptiPlex 9010.

After the computer is turned on, the computer is negothiating with my wifi router for speed and the LED on the wifi indicates a 10Mbps connection (the LED indicate it immediatly after power up). Once Win7 is booting up, there is no ethernet connection and in the windows device manager the ethernet controller is indicated as "not working properly".

In order to establish the ethernet connection I'm removing the driver and reinstall it, and a 100Mbps link is working properly as expected.

I've updated all the possible drivers from dell.com website.

One thing that I think is important is the BIOS version, which now is A05 on my computer and A12 is available.

I tried to install it several times, but when doing so, although there is no error messages, the computer is rebooting but the BIOS version stays A05...

What shall I do now? any suggestions?

Thank you,

Shay