Seeing the same problem. Had been using v1.15 since it came out with no reboot required unless settings change required it. Installed v1.20 the day after it came out. WAN access (and configuration access) totally froze up yesterday. Recycled power and all was well again.
Has all the symtoms of a memory leak issue within the router firmware. Using all default firewall and
WAN access settings. Using Comcast DNS, not advanced DNS.
Other than that firmware seems to working ok with 9 computers, a home server, 2 PS3's, and serveral printers on the local network.