Having disconnection problem with guest wlan, when OpenVPN client connects

Hi,
I am running tomato Shibby 116EN AIO on RT-N16
I made two following wireless networks to work

wl0(MainWireless-Bridged(br0) with Routers LAN ports,192.168.2.0/24 SSID:MainWiFi)
wl0.1(GuestWireless totally(br1) Isolated from the clients on br(0),192.168.3.0/24 SSID:GuestWiFi)

The Tomato configuration is as follows :
Basic -> Network ->LAN

Bridge STP IP Address Netmask DHCP IP...

Having disconnection problem with guest wlan, when OpenVPN client connects