I am using Iconics Graphworks with a celeron 800 mhz PC with windows 98 as the operating system, and the AB pktx card The PLC is a AB SLC/504. The problem I am having is that when I try to go into runtime I get a message saying that this programhas committed an illegal operation and will be shut down. If I cancel out of that the program will usually work properly for a couple of minutes then the message comes back. If I cancel out again and wait for a few minutes it somtimes comes back on its own. While it is not working if I hold the cursor on a tag it says: bad quality -communications failure or last known value. If anyone can help me with this I would really appreciate it.