For some reason my DIR-300 is stuck in booting just to Redboot. Although it might seem easy to fix, I have tried everything (from the obvious reconfiguration of the boot script, to repeating the full flash procedure and even tried the alternative DD-WRT Redboot).
It just won't boot the linux portion that holds the actual DD-WRT firmware.
JTAG may be a way to extreme measure, but it is guaranteed to work and I have already lost too many time trying to get this DIR-300 to boot again.
(BTW the issue appeared after I upgraded the firmware via the webif and then, after having the new firmware working, used the "Restore Factory Settings"... it never got past RedBoot again and the 30-30-30 is useless in this router, since it doesn't actually clear the nvram but instead enables me to go to the Redboot telnet prompt)