Drop in performance since changing the IP address of our SAP servers.

We have users all over Europe who have successfully been using GuiXT for many years. Last weekend we changed the IP address of our SAP servers, and most of our users are working normally, but a number of them based in Germany are suffering with performance issues on the GUI. If we deactivate GuiXT the screen navigation reverts back to normal. We have copied all the script files to a local test machine and pointed the profile to access these files but the performance is still slow. What could be the reason?

This sounds like a networking problem. Please check that all include files and all images that you use do indeed exist, since otherwise GuiXT will try to load them, and, depending on the network configuration, it can take a lot of time.