sorry for not getting back to you earlier.
Please can you try the following.
Can you Click on Start-> Run and type cmd.
Then type ipconfig /all and copy and post the text here.
Can you have a look in your Event Viewer and see if there are any error messages appearing. If so what are they.
Can you see if there are any new drivers for your Network Card. Download RadarSync
and this will tell you if there are new drivers available.