When trying to select a destination datastore (ESXi) or directory (HyperV) by clicking the "browse" button, we get this error message in VMX 6.7.1:
VMXFileManager.showBrowseDialog(): TypeError: _BACKUP_TASK is null
This is most likely related to this known bug:
The solution would be upgrading to at least 6.7.2 or to the newest version available (VMX 7 as of now).