I have had this problem very recently (literally yesterday) and every single thing I found pointed to just factory reseting, however there is one option you can try:
Go into Control panel in your network and sharing settings,
Then, open your specific network (i.e. if you're in windows 7, click where it says Local Area Connection in blue)
Third go to properties and click "Internet protocol Version 4" and then properties
set your static ip to what ipconfig says your router's ip is,
set your DNS to 8.8.8.8 and 8.8.4.4
Now try to access your router.
Im not sure how to translate this to windows 8 as I only use windows 7, but Im sure you can figure it out.
If this fails (assuming you did it correctly), you probably have to factory reset your router.