Master Green,
You need to provide more info.
So MASTER is acting as your LANs gateway... it's connected to your router directly via hardwired ethernet. MISSIE has some sort of USB wireless LAN connection, that can talk to MASTER.
My question: where is the switch? or in a wireless environment - the access point?
How is IP setup? does the Linksys router act as a DHCP server? does the Linksys router have an inbuilt wireless hub?
Maybe if I understood how MASTER and MISSIE were interconnected, I might be able to help.
I haven't played with wireless for ages.. but I'm pretty certain it's the same as wire. You've obviously checked the layer 1 connectivity - so they can all get a good signal. Now try layer 2/3, IF you have an access point that is acting as your switch/hub, is MERLIN obtaining an IP lease? or are you using static ips? can MERLIN ping MISSIE? by ip..
More info needed.
Good luck with it..
Lachlan
P.S Sorry I'm not familiar with Linksys products.. only Cisco.