Almost universally, this is caused by the PF Folder being placed on a network during the installation process.  In version 11.1.5 and earlier, the network style names are rejected by LXSoftware.  The solution is to map the network name to a local drive letter such as “Z:” and update the registry key for the PFDirectory (HKEY_CURRENT_USER\Software\Lafayette Instrument Company\LXSoftware\ExamPrefs\PFDirectory) and then restart LXSoftware.  A change in version 11.2 will allow network paths so this won't be an issue.