What is your operating system on new computer? Can you see SSID from router? My proposition switch off QSS and leave only Wireless Security (WPA2).

What is your connection with router (cable or radio)? If wireless connection give us screenshot from inSSIDer, installed on your computer. Jak łączysz się z routerem (kabel czy radio)? Jeżeli radio...

Give us screenshot from some speed test, made from your router.

In my opinion you can't change anything in this mode.

I thought that you have WR1043ND my proposition - Use WPS - NO click SAVE and Reboot your router.

Your software version on your article looks alot different to mine but have put in all the setting the same. Give us some screensgot from this menu in routera. Maybe switch off (disable) QSS in...