descomprimir o ficheiro em anexo (http://pt.tp-link.com/resources/software/TL-WR740N_V4_130322.zip) e executar:

scp wr740nv4_en_3_16_5_up_boot(130322).bin root@192.168.1.1:/tmp
ssh root@192.168.1.1
cd /tmp
mv wr740nv4_en_3_16_5_up_boot(130322).bin orig.bin
dd if=orig.bin of=tplink.bin skip=257 bs=512
mtd -r write /tmp/tplink.bin firmware

http://wiki.openwrt.org/toh/tp-link/tl-wr741nd#back.to.original.firmware

Anexo(s)