My recommendation is to backup your data then do a restore to factory new state. I don't know how you do this since that laptop is only sold in Brazil according to the Sony web site. That means I can't read the users manual, but you should be able to. It will tell you how to use the built in recovery partition if it has one, or the recovery DVD is it came with one or the recovery DVDs you created when you first got the computer.
I would also recommend buying an external hard drive and doing regular image backups so if this kind of problem happens again, recovery only takes 30 minutes or so.
If you don't want to do that, or at least not yet, try deleting the Marvel Yukon gigabit device from device manager then reboot. Win 7 will re-detect it and reload the driver which may resolve that problem.
Also schedule a chkdsk to run on the next boot, see if it fixes any file system corruption problems. Here is a write up I use for this:
How to run System File Checker (SFC) or chkdsk from the Recovery Console
Let this run to completion undisturbed..
- Boot your Vista or Windows 7 installation DVD
- When you see "Press any key to boot from CD or DVD", press Enter
- At the "Language" screen hold the "Shift" key and press the F10 key to open a Command Window
- Run SFC or chkdsk
- For sfc, type sfc /scannow and press Enter.
- For chkdsk, type chkdsk /r and press Enter.
Windows 7 only:
If you don't have a install DVD, you can download a legal copy here: Download Windows 7 ISO (Official 32-bit and 64-bit Direct Download Links) « My Digital Life
Make sure you get the same version you have installed: 32 or 64 bit; Starter, Home Premium, Pro or Ultimate.
I still recommend doing a restore to factory state though. Too many strange things happening with your system.