I would look at the other forum posts within the last day here, something occurred around 4:00 AM EST May 17 that looks to have caused some log fill up and while the error messages vary between model, the gist of it is that memory gets eaten up.
It looks to be the automatic update features, which even if they are turned off, the router still checks ASUS for info, and from what I can tell, it's getting a strange result back. The issue seems to have fixed itself today. There are several suggestion on the posts but what I found out helps me is to install a new firmware update.
After about 3 failed attempts to install the new firmware I found the following worked.
1. reset the modem back to factory defaults, make sure that you include the option to remove all files. You'll have to re enter the SSID name you chose and router ID / password.
2. On the firmware upgrade screen click on the link in"Please visit ASUS Download Center to download ASUS Firmware Restoration" That will take you to Asus's firmware download page.
3. Click on BIOS & FIRMWARE and download the firmware. In my case I was able to download it before my router disables, but you may have to directly connect to via your ISP modem's.
4. Unzip the file
5. Once you get the firmware, click on "Manual firmware update : Upload"
6. Then reset the router back to factory defaults and redo SSID and username / password.
