A hotfix has been released for Navisworks 2014 and is now available for download from the Autodesk Website.
NWF refresh issue hotfix
This hotfix is designed to resolve an issue where Navisworks Manage and Simulate may close unexpectedly when refreshing a NWF. Please note, this hotfix requires Navisworks 2014 Service Pack 1 to be installed.
The hotfix can be downloaded from here: Navisworks 2014 SP1 NWF Refresh Hotfix.