Nope, not overclocked and no passwords have been changed either. It's really strage, this morning it was fine, I haven't changed anything at all today. It' like the internet hardware of the phone has just stopped working

Totally remove the wifi saved settings and try again
try disabling wifi power saving
the hardware hasn't totally stopped working if it can scan networks, at least the driver is there, although maybe broken, and it can sure receive fine.

How do I remove the wifi settings and disbale power saving?

system > settings > connectivity > internet connections
press connections button and delete whichever one you want to connect to, then hit new, put it back in, and theres an advanced setting you can disable the power saving mode while you're doing that.

if that doesn't work, i would try to reinstall osso-wlan and the wl1251 driver, but i don't know the commands. especially if you can't connect, someone has to cough up the files you require since you can't use apt-get. maybe try to download lxp's injection driver stuff, it should replace both of those with slightly different versions. you can find a rapidshare link if you scour his thread.