The IP of the bridge is occasionally unavailable

When using VLAN’s, you should create an /interface/vlan for management purposes. And…the bridge should not have an IP address when using VLAN filtering. My best guess is that it does, but that would require the config for confirmation.

Don’t know if you are familiar with this great topic:
http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1