Can you change this:
/ip address
add address=192.168.1.101 interface=PLC-vlan-4 network=255.255.255.0
to this:
/ip address
add address=192.168.1.101/24 interface=PLC-vlan-4 network=192.168.1.0
Also, please consider going VLAN all the way:
http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1