A common technique for troubleshooting applications on both Windows and Macintosh is to check for a corrupted preferences file. The Prefs file for an application typically stores the settings of any customizable features between runs, and if it becomes corrupted it can cause an application to crash or otherwise misbehave. The easiest way to diagnose Prefs file trouble is to remove the file(s) from where the application is expecting to find it, thus causing the application to recreate a default Prefs file from scratch.
Under Windows, 4D Applications store their Prefs inside of the active Windows directory (e.g. "C:\Windows" or "C:\Winnt"), inside of a directory named "4D". You can safely trash the entire contents of this directory on a PC with the exception of the "Network" directory which must contain at least one Network Component for use with 4D Server. Registrations are kept in the Windows Registry, so you need not worry about finding your serial numbers if you clear the 4D folder.
Under Macintosh, 4D Applications store their Prefs inside of the active system's preferences folder (e.g. "Macintosh HD:System Folder: Preferences"), inside of a folder named "4D". You can safely trash the contents of this folder with the exception that you will lose your registrations and must re-enter your serial numbers. However, you need not worry about losing the Network Components because on a Mac they are stored inside of the individual 4D applications that use them.