wifi problem topic

Hello,
i own a RK3188 device (T-R42 with board version B351 V1.1)
I flashed a custom rom and since then i am no more able to reactivate the wifi
I tried many other custom roms and stock roms, but i have always the same behavior:

When from the settings i try to turn it on, it stays on for a few seconds ( no wireless network is shown ), and then it goes off

This is the logcat that is printed when i try to turn my wifi on:
(using command adb logcat on terminal emulator session)

D/WifiHW ( 368): Read wifi chip type OK ! wifi_chip_type = RK901
D/WifiHW ( 368): wifi_load_driver: DRIVER_MODULE_PATH = /system/lib/modules/rkwifi.ko, DRIVER_MODULE_ARG =
D/BluetoothAdapterService(1097373104)( 811): getState(): mAdapterProperties: com.android.bluetooth.btservice.AdapterProperties@ 4168aef0
D/BluetoothAdapterService(1097373104)( 811): getState(): mAdapterProperties: com.android.bluetooth.btservice.AdapterProperties@ 4168aef0
D/WifiService( 368): setWifiEnabled: true pid=870, uid=1000
D/AudioHardwareALSA( 109): Audio exiting sandby will open audio device
D/AudioHardwareALSA( 109): AudioStreamOutALSA::standby().....
D/WifiHW ( 368): wifi_load_driver: driver load failed
D/WifiHW ( 368): Unable to unload driver module "wlan": No such file or directory
E/WifiStateMachine( 368): Failed to load driver!
E/WifiStateMachine( 368): DriverFailedState

i checked that under system/lib/modules do exist these files:
rkwifi.ko
wlan.ko
both with owner 'root', group 'root' and permissions 644

Can someone give me some hints on what is the possible cause of this error,
and how to discover the right wifi drivers for my device?

Thank you!