Friday we've had a go at the Kawasaki robot to try some solution for the communication problem.
After an update to the latest firmware version we were not able to get the gateway to work on port 1. Strangely when we tried communication on port 2 id did work. (don't ask why we tried)
For test reasons downgraded the robot to the old firmware and tested the gateway connection on port 2. This also worked. As you can imagine, we we baffled.

Don't know for sure any more if we've ever tried to get the gateway working on port 2 in the first place, but at least we've got a working solution for the moment.
[UPDATE!!!]
Just upgraded the robots to the latest firmware version.
*=== AS GROUP === : ASE_010000V1Y 2011/10/13 22:44
*=== SERVO GROUP === : SVE_08000000W 2010/06/11 15:10
Now I can enter 1 gateway adres. A popup box will appear when entering gateway data for the other port. It's tested and now I have gateway communication on the port I've entered the gateway data.
Now some new options are availeble. Haven't checked them out yet. I'm only glad the upgrade went without any major problem.