What PLC are you using? What device is giving you this fault? You are probably going to need to provide a lot more information if you expect to get any help. I am guessing you are having a problem with a PanelView 800. I found this in the Rockwell knowledgebase. You will need to have a free account to view it. ID: BF12651 | Access Levels: Everyone. There are other articles there that are access level everyone, take a look through there and see if it helps.