I use C3D 2011. I have a "master design" file for my drain network. I make a data shortcut of this network to use in a separate file where I create my plan and profile for each street of my master design network. Although no changes have occurred to either file since I last opened these drawings, on occasion when I open up the street drawing some or sometimes all of my pipes will be missing from the profile. They are still there in the plan view in both the master design and the individual street drawing. If I close out of C3D without doing anything my pipes will show up eventually in the profile. Sometimes I have to do this process two or three times before the pipes show back up in the profile. Has this happened to anyone else? Any thoughts? I cannot readily duplicate the problem and it does not happen all the time just sporadically.