I have had issues for some time now where the Predecessors disappear from the task box. I double click on a task and select the Predecessors tab and it’s blank. When I close the box, the Predecessors and Successors are listed in the task like. Sometimes it switches from SS to FS and creates havoc with the dates. This is a random issue. We use SP heavily, but I have my copies stored on My Documents as well as my desktop.