You're having a memory leak issue. If you're willing to poke around in Telnet, you can find out what is causing the problem. I have a GT784WNV with the same problem and I have a suspicion it is both the DHCP Daemon and the WLAN daemon causing problems.
To check the memory usage:
Download PuTTY: »
www.chiark.greenend.org. ··· oad.htmlIn PuTTY, set the connection type to "Telnet" and punch in your modem's IP address.
Hit "Open"
A login prompt should appear. Enter in the username of admin and the password of admin. If that doesn't work, try the same username and password combination used for the web interface.
At the command line, type in the command: free -m (or just free)
The Gateway should then spit out a bunch of information concerning memory usage. To copy/paste that info to a post, highlight the text you want, and PuTTY will automatically copy the text to your clipboard.