On my Vaio wireless was working perfect for about a year untill I ran some Vaio update. After that started wireless connection going down pretty often.
Not sure if we have the same problem and if this is a perfect way of doing it. I'll just tell what I'm doing to restore connection. It's a kind of a headache, but eventually can do it pretty fast.
1. On the toolbar double click the Vaio Smart Network icon (if you have one).
2. On the Smart Network window click WLAN check box if it's not green.
3. Click Settings.
4.On WLAN tab select the profile of your connection (again if you have one, if not create a profile on Advance Settings)
5. Click Switch Profile (wait while it's switching)
Don't close this window yet. Check if the connection icon on the
toolbar changed to the one with the globe. If it did try to
open a browser to see if it's working.
If still no connection:
6. Click Diagnose button.
Usually diagnose ends up with a couple of option, one of them to
import IP addresses. Click to Import. After that it gives the
message that problem resolved.
Usually after that I get connected. Good luck.