Linksys wireless router within network

I can't tell exactly what you're doing wrong from your description. It's better to describe how to do it right and not try to diagnose whatever is going wrong. What you want to do is convert your BEFW11s4 wireless router into a wireless bridge (i.e. no router).

1. Do not plug anything into the WAN port.
2. Connect to the BEFW11s4 and configure the LAN IP address to be an unused static IP address in the office LAN range. That would be

10.0.0.xxx or whatever. Make sure you don't pick something that's in the office networks DHCP range, or is duplicated.

1. Disable the DHCP server.
2. Connect a CAT5 cable from the office LAN switch port to one of the LAN ports on the BEFW11s4. Make sure the polarity is correct by checking the lights on the front of the BEFW11s4.

Congrats. You now have an access point. You should be able to access the wireless configuration at the IP address assigned in step 2. IP addresses to the clients will be delivered by the office DHCP server (not the BEFW11s4). Security (authorization and authenticaion) is your problem as I have no clue what your office LAN is using. Since an access point is a bridge and not a router, it knows nothing of IP addresses and should therefore be transparent to the network. All the shares should be visible.

Thank you kindly, Jeff... that did it.

You're the man!