I have searched the forum, but can't find the exact same problem.
I use the MBW with Twonky as NAS to play audio on my Denon receiver. For years this did work without a flaw. The MBW had a static IP-adress (192.168.50.52), used range is 192.168.50.50 ~ 192.168.50.80. Starting from 192.168.50.60 the addresses are handed out by DHCP. Some time ago connection was lost to the MBW, which could be solved by switching on and off the unit. Recently this didn't help anymore. I than decided to reset the MBW and there it was again with an IP-address out of the DHCP-range. But the next day it was gone again.
So if I want to listen to some music I have to reset the MWB and than it works for a while. I changed my router-settings so the MBW always gets the same IP-address based on its MAC-address, but the same result.
Hardware (LAN-port) issue?