Thanks for the update OscarMartiH 
Are you aware that Windows 8 and 8.1 have an improved version of Windows Defender that offers the same real time protection as Microsoft Security Essentials, you do not need a third party AV installed and not having one reduces the chance of software conflicts, it is your decision entirely but we may need to have you uninstall eset and use Defender as part of the troubleshooting process.
Can I ask if it would be possible for you to connect the notebook to an ethernet connection so that you can turn off and uninstall the wireless card drivers and then test the computer by using the ethernet connection as opposed to the wireless connection, if you have no issues it suggests the wireless device/drivers are the problem, if the problem is still present it may suggest that eset is the cause.
You are welcome btw 
NB: So that I can confirm that you have received notification of my reply to your topic please click on the Follow this topic tab at the upper right corner of the page.