Nothing's wrong but can't connect to the internet

So yeah, my router has been working perfectly fine (most of the times) until yesterday.
I've not changed any of my router settings from when it was working.
My modem is working perfectly fine, right now I'm connecting it straight from the modem and not through the router.
I've tried with another computer,laptop and phone but the result is the same.
In the Status of the router it says connected but I can't connect to the net nor does anyone else.
I've tried restarting it a lot of times through the settings from the browser(haven't tried poking it) but still can't connect. In my network and sharing center it says it can connect to the internet while I don't.
It works perfectly fine without the router.
All the lights on the modem is flashing like normally.
I think it's not the ISP's fault because I can connect with my modem.
I've tried disabling the firewalls but same thing.

Please help and thanks a lot

.::EDIT::.
Sorry, I forgot to tell you my Router, it's an Asus WL520GC and some Motorola Modem (SB5100)

Try this:
1) Turn off the computer, unplug the modem and the router.
2) Plug in the modem and let it sync up.
3) Plug in the router and let it sync with the modem.
4) Start your computer.

If you get no joy, you can set the router back to it's default setting and try again. You should also make sure the router has the latest firmware.

Well I restored to factory defaults and i reconfigured the router but it didn't work. But the next day I could connect to the internet although I don't know what happened.