Hello,
I use RB951G-2HnD at home, no special things is configured. There is PPPoE connection to an ISP, only one firewall rule in NAT for masquarade srcnat. On my notebook I try to connect VPN, using Network Manager in Ubuntu (it is an OpenVPN connection) . Everything is going OK, but in serveral seconds after connecting network on notebook became unreachable (VPN routes still present, but VPN server is not pinging). Seems like router droped VPN connection, because to check the issue I reinstalled my old router and everything worked well.
I tried reseting router configuration then used standart Quick set and configured it as Home AP, the problem still existed.
Is there way to track where is the problem? Several days of googling and experementing didn’t give me any clue 
Current settings is:
# dec/06/2015 16:09:57 by RouterOS 6.33.3
# software id = S6M7-1D55
#
/interface bridge
add name=br1-wan
add name=br2-lan
/interface ethernet
set [ find default-name=ether1 ] name=eth1-wan
set [ find default-name=ether2 ] name=eth2-wan-iptvbox
set [ find default-name=ether3 ] name=eth3-lan
set [ find default-name=ether4 ] name=eth4-lan
set [ find default-name=ether5 ] name=eth5-lan-comp
/interface pppoe-client
add add-default-route=yes disabled=no interface=br1-wan max-mru=1480 max-mtu=1480 mrru=1600 name=pppoe-out1 password=*** use-peer-dns=yes user=***
/interface wireless security-profiles
add authentication-types=wpa2-psk eap-methods="" management-protection=allowed mode=dynamic-keys name=wpa2-protect supplicant-identity="" wpa2-pre-shared-key=***
/interface wireless
set [ find default-name=wlan1 ] disabled=no mode=ap-bridge security-profile=wpa2-protect ssid=my_ssid wireless-protocol=802.11
/interface wireless nstreme
set wlan1 enable-polling=no
/ip pool
add name=dhcp-local-pool ranges=192.168.1.100-192.168.1.200
/ip dhcp-server
add address-pool=dhcp-local-pool disabled=no interface=br2-lan lease-time=8h name=dhcp-lan
/interface bridge port
add bridge=br1-wan interface=eth1-wan
add bridge=br1-wan interface=eth2-wan-iptvbox
add bridge=br2-lan interface=eth5-lan-comp
add bridge=br2-lan interface=wlan1
/ip address
add address=192.168.1.1/24 interface=br2-lan network=192.168.1.0
/ip dhcp-client
add default-route-distance=0 dhcp-options=hostname,clientid disabled=no interface=br1-wan
/ip dhcp-server network
add address=192.168.1.0/24 dns-server=192.168.1.1 gateway=192.168.1.1 netmask=24
/ip dns
set allow-remote-requests=yes
/ip firewall nat
add action=masquerade chain=srcnat out-interface=pppoe-out1 src-address=192.168.1.0/24
/ip upnp
set enabled=yes
/ip upnp interfaces
add interface=pppoe-out1 type=external
add interface=br2-lan type=internal