Error "Reference_Id.lbl : Could not Open File : errno -1."

Getting this error every once in awhile, completely locks up the program, usually means I need to restart the system as after I clear all these errors and PC-DMIS shuts down, I can't even get into Task Manager.

PC-DMIS 2011MR1, on a Windows XP system. And it's the NC Server (Image might be a little too small, the error message is really all thats there).

The thing that puzzles me, is that every once in awhile, PCDMIS will lose reference of the CAD models associated with the program, and generate reports with no models. I've attributed this to the fact that everything is located on the network (I know, I know...). However, these files are PCDMIS installed files which are located on the hard drive, so how would PC-DMIS all of a sudden not be able to open or access said files?

Any insight into this would be appreciated, thanks again.