First why 2 bridge and using vlan? As a newbie I’ve been there long time ago, always make 2 bridge (or more zZz) just to make another netwok segment.
Now with vlan no need many bridge anymore, just one and next can create more than one network segment.
/interface bridge
add name=ACCESS_999
add name=LAN
Just one bridge then put all your ethernet port into that single bridge.. Let say you choose to use only LAN bridge, delete the ACCESS_999 bridge entry.
/interface bridge port
add bridge=ACCESS_999 interface=ether2
add bridge=ACCESS_999 interface=VLAN_999 <= as anav mention this make that error about slave. Only entry ethernet port and/or wlan with corresponding match pvid.
since u delete ACCESS_999 bridge, change it to
/interface bridge port
add bridge=LAN interface=ether2
/interface vlan
add interface=LAN name=VLAN_101 vlan-id=101
add interface=LAN name=VLAN_201 vlan-id=201
add interface=LAN name=VLAN_999 vlan-id=999
The rest I think you must know about tagged and untagged, firewall etc. You can read nice tutorial here http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1
Your config above not complete.