Basically you've got 2 possibilities. It's a software problem, or it's a hardware problem. If it's a hardware problem, there is not much you can do, unless you've got golden hands.
A software problem divides in 2, degraded flash, or b0rked up configuration. If the flash is degraded you should reflash it. If the 'network_telnet_stop' script does not work for you, the only way to do so is using serial and the bootloader. Basically you have to upload a kernel using tftp, boot that, and let it flash firmware from an USB stick. More here
If it's configuration, then the 'network_telnet_stop' script should definitely work, as it's invoked before the configuration is read.