How do I get my Watchguard VPN clients to see the two distinct networks attached to my trusted interfaces? They can only access the one.

The firmware is XTM 11

Give this a try: add an Any rule where the From is Firebox and the To is 192.168.131.0/24. If that works, you can tighten the rule down by only allowing specific ports, if you want. If it doesn't work, check Traffic Monitor while you're trying to access the 192 network for any deny messages.

Tried and no luck.  

Checked out the traffic monitor while attempting to ping.  The only messages that are related to the IP of the VPN client are these:

2009-09-08 14:44:55 Allow 10.247.131.232 10.247.131.5 dns/udp 64702 53 0-External 1-Trusted Allowed 62 127 (Great Slave IPSEC-Any.in-00)  proc_id="firewall" rc="100" src_user="Jeff_Denomme@Firebox-DB"       Traffic

2009-09-08 14:47:42 Allow 10.247.131.232 10.247.131.5 netbios-ns/udp 137 137 0-External 1-Trusted Allowed 78 127 (Great Slave IPSEC-Any.in-00)  proc_id="firewall" rc="100" src_user="Jeff_Denomme@Firebox-DB"       Traffic

It doesn't look like this is even related to the ping request.  .5 is our DNS server

I forgot in 11 they moved handling of muvpn traffic to the external interface. Let's try this (delete the previous rule if it's still there): add Any rule where From is <netrange of muvpn clients> and To is 2-Trusted (that's assuming the 192 network is aliased to 2-Trusted. Otherwise use 192.168.131.0/24.).

Hmm, still no luck.  Is there more that might need to be done in the settings for the muvpn?  Seems like I've exhausted all the possible policy settings (However, I am not sure about this and am open to any suggestions!)

I just noticed the tab in the policy manager labelled "Mobile VPN with IPSec", so I changed the existing Any policy to include access to the remote network 192.168.131.0/24........... Saved it and tried pinging the network again with no luck.

This is frustrating! ;)

Does traffic monitor provide any additional information after updating the muvpn policy?

This is what is shown after updating the policy manager:

2009-09-08 20:26:59 sessiond Management user admin from 10.247.131.27 logged in id="3E00-0002"       Event
2009-09-08 20:27:00 Deny 10.247.131.84 140.90.113.200 http/tcp 4894 80 1-Trusted Firebox tcp syn checking failed 40 128 (Internal Policy)  proc_id="firewall" rc="101" tcp_info="offset 5 AF 1142210966 win 47869"       Traffic
2009-09-08 20:27:02 configd SYNC configd_pushnewfile: "/pending/config.2740.9.cfg" OK, sending notifications        Event
2009-09-08 20:27:02 sslvpn Result received on ipc socket:         Event
2009-09-08 20:27:02 sessiond Management user admin from 10.247.131.27 logged out id="3E00-0004"       Event
2009-09-08 20:27:03 pptp dd_client state dd_client_config_change        Event

Sorry for the delay. I actually started working a similar issue yesterday for a customer. I'll let you know what I find.

Please do!  I am still at a loss.  To work around the problem I created two separate VPNs for each network and gave users access to the one that is most relevant to them.  However, I would ideally like to make both networks accessible through the one VPN.