Protool Runtime Problem

Can anyone help with with an issue I have been having for about 6 months? I have protool runtime running on a sinumerik 840di machine operating a threader but every so often the runtime will lock up and show only #### signs. We have had the machine rebuilt, re-installed all software from scratch and even bought a new hard drive for the 840di. We have also checked all profibus connectors and cables but still we have the same problem. Does anyone have any ideas or know the cause and solution to this?

When there is a comms problem for example, there appears a system message with an error code. The error code will tell pretty precisely what is wrong - in most cases.
If the message disappears before you get the chance to see it, then go to a message view that displays all system messages. If you dont have such a message view, then add such a message view to the project.