If a FontLab application is behaving strangely, sometimes resetting the app preferences may help. 

If the problem is in FontLab VI, you can use the "hamburger" menu in the Preferences dialog to reset all settings to their defaults. 

If that doesn’t help, or you are using a different FontLab application, you can also do it manually by removing the preferences file.

Mac

On Mac, All Fontlab apps keep their preferences in the user's ~/Library/Preferences folder. To remove the preferences file correctly:

0. Quit the application (FontLab VI, Fontlab Studio, TypeTool, etc.).

1. Open the folder ~/Library/Preferences/. The user's Library folder is hidden. But you can reach it using the Finder's Go menu with the Alt key pressed.

2. Find the corresponding file with the .plist extension starting with "com.fontlab". For example, FontLab VI keeps preferences in com.fontlab.fontlabVI.plist.

3. Move the file into the Trash.

4. Run Terminal, put the following command after the prompt and press Return:

killall -u $(whoami) cfprefsd

Explanation of step 4: macOS caches preferences (since 10.9). The service doing the caching is called "cfprefsd". Thus, after you delete (or change) the plist file you need to run the above command in the Terminal window. Otherwise macOS will restore the cached preferences.

Windows

On Windows, preferences reside in the system registry. To wipe preferences out from the registry:

0.  Quit the application (FontLab VI, Fontlab Studio, TypeTool, etc.).

1. Run the utility for editing system registry regedit.exe.

2. In the left part of Regedit window, open HKEY_CURRENT_USER\Software\Fontlab section.

3. Click on the section called "Studio 5" or "fontlabVI" or whatever prefs you want to remove and choose Edit > Delete (or press the Del key).

4. Confirm deletion of the section.