try reinstalling ur windows again..sometimes it happens with the drivers.specially with wireless lan..i had the same problem last week...created backup and deleted all the partitions of the hard disk and reinstalled windows with new partitions..now it works fine....these type of error usually comes beacuse of viruses...most of the antivirus are unable to detect some particular type of viruses till now...not even 1 antivirus works 100% :(