Hi,
There isn't much specific info about WR741nd TP-Link router

I managed to patch firmware from trunk 
http://downloads.openwrt.org/snapshots/ … pgrade.bin

This time around it works with DHCP, and it's acutally working fine apart from wireless.:

first firmware update I did via GUI.

Last one from console

ssh 192.168.1.1

cd /tmp
wget http://mylaptopIP/NewFirmware.bin
mtd -e firmware write /tmp/NewFirmware.bin firmware && reboot

and reboot
and login with telnet

I did afterwards
opkg update
opkg nano
opkg screen
(some basic progs)

opkg kmd-ath9
(wireless module)

nano /etc/config/wireless
pasted following config
###my sample config
config wifi-device  wlan0
        option type     mac80211
        option channel  1

config wifi-iface
        option device   wlan0
        option network  lan
        option mode     ap
        option ssid     MYSSID
        option encryption psk2
        option key      MyPass
##endof config

#started wifi with

wifi on
=> but it doesn't work
outpu:__________________________
PHY for wifi device wlan0 not found
PHY for wifi device wlan0 not found
_______________________________

output from logread is
__________________________________
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_send_assoc_timeout
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_scan_done
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_send_auth_timeout
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_remain_on_channel_expired
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol ieee80211_amsdu_to_8023s
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_send_deauth
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol __cfg80211_send_deauth
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_new_sta
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_ready_on_channel
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_rx_action
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_classify8021d
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol wiphy_register
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_action_tx_status
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol wiphy_new
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_put_bss
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol ieee80211_bss_get_ie
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_ibss_joined
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol __cfg80211_send_disassoc
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_michael_mic_failure
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_send_rx_auth
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol wiphy_unregister
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_send_disassoc
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol ieee80211_radiotap_iterator_init
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol __cfg80211_auth_canceled
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_get_bss
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol __ieee80211_get_channel
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol rfc1042_header
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol ieee80211_data_to_8023
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_send_rx_assoc
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol ieee80211_radiotap_iterator_next
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol ieee80211_channel_to_frequency
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol ieee80211_hdrlen
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_inform_bss_frame
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol ieee80211_frequency_to_channel
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol bridge_tunnel_header
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_unlink_bss
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol wiphy_free
Jan  1 00:02:45 bs6 user.warn kernel: mac80211: Unknown symbol cfg80211_cqm_rssi_notify
Jan  1 00:02:45 bs6 user.warn kernel: ath: Unknown symbol wiphy_apply_custom_regulatory
Jan  1 00:02:45 bs6 user.warn kernel: ath: Unknown symbol freq_reg_info
Jan  1 00:02:45 bs6 user.info kernel: Generic kernel compatibility enabled based on linux-next next-20100113
Jan  1 00:02:45 bs6 user.info kernel: cfg80211: Calling CRDA to update world regulatory domain

I've been compiling from source / trunk and the wireless config was :

config wifi-device  radio0
        option type     mac80211
        option channel  5
        option macaddr  <device mac>
        option hwmode   11ng
        option country  GB
        option htmode   HT20
        list ht_capab   SHORT-GI-40
        list ht_capab   DSSS_CCK-40
        option disabled 0

config wifi-iface
        option device   radio0
        option network  lan
        option mode     ap
        option ssid     '<SSID>'
        option txpower  17
        option isolate  1
        option encryption none

Note that build was from post 9.0.2   (r20120)