Question : Issues routing through Juniper SSG 140

We have a Juniper SSG 140 that we just put in recently but we are having issues with it and it not playing nicely with some things but not others.  In addition to the SSG between us and the internet we also have and Cisco 1800 router for our MPLS connection to our other office. All the desktop and laptop computers in the office don't have problems connecting to things on the far side of the MPLS.  What does have a problem are the Toshiba phone systems and the 5250 emulations on the thin clients that we have for our production area.  If we set the default gateway to the MPLS router everything is fine.  If we set it to the SSG then the phone system won't connect at all and the thin clients will connect and run fine for about twenty seconds then disconnect.  We have an entry in the destination routing table to route any traffic from the LAN thats destined for the other office through the MPLS router but still something is wrong or missing.

Answer : Issues routing through Juniper SSG 140

Sounds to me like a session timeout issue, which can occur if traffic is flowing only into one direction using SSG. The returning traffic is let into the LAN immediately, I suppose, instead of passing SSG again. Either the Cisco has to transfer all traffic for local to SSG, and SSG is default gateway; or Cisco is default gateway, but passing all non-related traffic to SSG, which does Internet.

IMHO best config would be SSG as default gateway, Cisco for MPLS connected to an own interface on SSG.