I've been working on an Autocad piping project for a few days now, in Autocad MEP 2011. I've been using butt welded steel pipe and it was working perfectly fine until today. Today, when I started up Autocad, for some reason, when I tried to place pipe or fittings, there were only 5 or 6 different pipe types to choose from. A LOT less than usual. Additionally, almost all of the fittings and valves were missing, so I could no longer find the parts i needed for my project. However, the pipe, fittings, and valves I in the model earlier are still there, so I figure the program can't be having trouble accessing the model files, it must just be a problem with the catalog. What might be causing this problem and how can I fix it?