Yep, I have been suffering for 2 months with this on my Duo 11. It used to be perfect then the ethernet driver failed first running from 39mps down to between .5 - 1.5
I then started using the wireless only, which worked fine, then went the same way.
I have done everything to rectify it, but was advised back in August by Sony that there had been an issue with a Windows 8 update around the time and the driver was not able to cope, so they were writing a fix. I was told this would be done by the end of August, but that wasn't the case. I phoned support again two weeks ago after getting frustrated with waiting and was told they are working on it and would be released at the end of the month. Well it's the end of the month and I have just checked for updates in Vaio care and nada!! If this prolongs I will also concider returning it and posting my displeasure where I can. I am a massive Sony fan (computer, phone, amp, gaming, camera etc) usually, but this has gone beyond the joke. Currently Vaio products are not fit for purpose. I was going to pre-order a PS4 and get a Smart Watch 2, but my current disatisfaction has caused me to reconcider both. Maybe I will chop it in for an Acer and used the saved money for an xbox one....
