It is generally advised not to use multiple bridges unless you really know why you need it. It can be a shortcut solution but it’s not optimal performance wise (only 1 bridge can be HW offloaded and you will not know in advance which one) nor suited for future adaptation. For 2 subnets, it may do.
Your device does not know where to go to…
I suppose you did not define the needed route towards the other subnet ?
Add route for 192.168.77.0/24 gateway bridge1
You also may have to revise your firewall rules to allow communication between both subnets.
Better approach (a bit more work to setup but more future proof and can, for some devices, benefit from HW offload) is to use VLAN, one per required subnet.
Check this excellent tutorial from member pcunite:
http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1