Two users accessing one file 08.11.07.443

We have had an odd occurrence several times now.  Two users accessing the same file with write permissions (not read-only) at the same time.  I was just wondering if anyone else has seen this. Both are running InRoads, however, they are opening the file in plain MicroStaton before initiating InRoads.  This at some point produces and exception error and knocks them out of MicroStation.