rb951ui-2hnd Wi Fi N network

hi, my notebook connected to Wi Fi network.

in Band 2Ggz-only-G and 2Ggz-b/g it’s ok, but 2Ggz-only-N and 2Ggz-B/G/N connected for a while and the connection is lost.
network status connected but without access to the Internet
ping status router and other resources to lost

the same problem iPad.

Help me…
Sorry my bad english.
WiFi_Statuspng.png
WiFi_Adv.png
WiFi_Wierless.png

Hello, on “HT” its both chains selected? 0 and 1
chaine.png

As far as I know we have 2 antennas.
WiFi_HT.png

heeelp, do what I with it?

Update to the latest RouterOs and latest Bios.
http://www.mikrotik.com/download/share/routeros-mipsbe-6latest.npk
Go to new terminal and reset wireless settings with command
/interface wireless> reset
Her configure wireless settings

still lost the connection (

 max-rtt=99ms 
HOST                                     SIZE TTL TIME  STATUS                 
192.168.101.70                             56 128 2ms  
192.168.101.70                                          timeout                
192.168.101.70                                          timeout                
192.168.101.70                                          timeout                
192.168.101.70                                          timeout                
192.168.101.70                                          timeout

What see you in log file?

See on my website to add wireless debug in logfile but is in dutch.
See the printscreens a made
http://www.wirelessinfo.be/index.php/mikrotik/pages/logging

Here a website that explane wireless problems
http://wiki.mikrotik.com/wiki/Wireless_FAQ
Maby see you there the wright solution

set up, wait

in the main logs:

15:[b]15:33[/b] wireless,info 94:DB:C9:3E:15:6A@wlan1: connected 
15:[b]16:31[/b] wireless,info XX:XX:XX:XX:XX:XX@wlan1: disconnected, group key exchanimeout (this time not connected)
15:16:31 wireless,info 20:16:D8:1F:90:05@wlan1: connected

debug

15:31:31 wireless,info 20:16:D8:1F:90:05@wlan1: disconnected, group key exchange timeout 
15:31:32 wireless,debug wlan1: 20:16:D8:1F:90:05 attempts to associate 
15:31:32 wireless,debug wlan1: 20:16:D8:1F:90:05 not in local ACL, by default accept 
15:31:32 wireless,info 20:16:D8:1F:90:05@wlan1: connected 
15:36:32 wireless,info 20:16:D8:1F:90:05@wlan1: disconnected, group key exchange timeout 
15:36:33 wireless,debug wlan1: 20:16:D8:1F:90:05 attempts to associate 
15:36:33 wireless,debug wlan1: 20:16:D8:1F:90:05 not in local ACL, by default accept 
15:36:33 wireless,info 20:16:D8:1F:90:05@wlan1: connected 
15:41:32 wireless,info 20:16:D8:1F:90:05@wlan1: disconnected, group key exchange timeout 
15:41:33 wireless,debug wlan1: 20:16:D8:1F:90:05 attempts to associate 
15:41:33 wireless,debug wlan1: 20:16:D8:1F:90:05 not in local ACL, by default accept 
15:41:33 wireless,info 20:16:D8:1F:90:05@wlan1: connected

how can I fix it?