Paint Shop Pro 5.03's main window doesn't appear when started from the start menu

PSP 5 installs fine and can be updated to 5.03. When starting it from the start menu, the splash screen and the tip window appear. But the main window doesn't. The PSP.EXE process is running and can be killed. However when PSP is started from the context menu of the "My Computer" desktop icon, the main window appears. A video demonstrating this is attached to this ticket.