Please determine what frequency or channel your router is on:
sudo iwlist wlan0 scan
If, for example, your router is on channel 13 and your wireless driver either doesn't know or guesses what country you are in and guesses USA where channel 13 is impermissable, you might not see your router. I recommend that your regulatory domain be set explicitly. Find yours here: http://en.wikipedia.org/wiki/ISO_3166-1_alpha-2 Set it permanently:
gksudo gedit /etc/default/crda
Use nano or kate or leafpad if you don't have the text editor gedit. Change the last line to read:
Of course, substitute your country code if not Iceland. Proofread carefully, save and close the text editor.
Next, if your router is set to use N speeds exclusively and your wireless device doesn't do N, I doubt you will see your router. I recommend you set your router to B, G and N speeds.
WPA2-AES is preferred; not any WPA and WPA2 mixed mode and certainly not TKIP. Second, if your router is capable of N speeds, I have better luck with a channel width of 20 MHz in the 2.4 GHz band instead of automatic 20/40 MHz. I also have better luck with a fixed channel, either 1, 6 or 11, rather than automatic channel selection.
If these changes are ineffective, then we should look at the driver for your wireless device. Please show us:
lspci -nn | grep 0280