here i'll explain very simple how to setup a telnet daemon, so you can telnet to your router

BE CAREFULL, PORT 23 WILL BE EXPOSED TO YOUR WAN TOO!!!!
THE TELNET DAEMON DOES NOT ASK FOR A PASSWORD!!!

step one: setup your FTP to access your root, can be found in the HTT Forum

step two: upload those files to the /tmp/ directory in your router
http://files.wl500g.info/asus/wl500g/telnetd/busybox
http://files.wl500g.info/asus/wl500g/telnetd/telnetd

if this doesn't work upload those files too:
http://files.wl500g.info/asus/wl500g/telnetd/faucet
http://files.wl500g.info/asus/wl500g/telnetd/modules
http://files.wl500g.info/asus/wl500g/telnetd/mysh
http://files.wl500g.info/asus/wl500g/telnetd/strace

step three: perform those four commands, and you are ready to telnet to your router: telnet://my.router

chmod a+x /tmp/busybox
chmod a+x /tmp/telnetd
ln -s /tmp/busybox /tmp/sh
/tmp/telnetd -d -l /tmp/sh &

to perform those commands:
open up the 'System Command' page at
http://my.router/Main_AdmStatus_Content.asp
fill in the command you wan't to execute
and push the Refresh button (DO NOT hit the enter your keyboard, the command won't be executed then)