With enough models and XREFs its possible that multiple users could be calling the refresh function at the same time, causing the same NWCs to be rebuilt from the source DWGs by multiple computers. As far as I can tell, NavisWorks doesn't check to see if the NWC is already opened by another computer when it attempts to update that NWC, resulting in crashing and/or generating files along the lines of Model1.nwc~, Model1.nwc~~, Model1.nwc~~~. I'm not sure if it loads one of these new files or the actual Model1.nwc file but they shouldn't be created in the first place.

NavisWorks (all NWC-generating versions) should check to see if the NWC file can be opened for writing *before* it attempts to update the file. If it isn't, wait for a pre-determined time, after which if the NWC file still needs updating and cannot be opened for writing alert the user with an option to either skip updating that file or to try again. The time-out period, on the order of 2-5 seconds, would be configurable from the global options dialog. Alternatively, a locking file similar to the DWL2 (such as creating an NWL2 file during the update process) could be implemented.