Problem solved! I first tried with another user directory: C:\Programmer\LyX14\bin\lyx.exe -userdir C:\Programs\LyX
That worked. I then deleted my original userdir: c:\Documents and Settings\taa\Application Data\lyx1.4.x Then I tried starting the program up again without the -userdir switch. The c:\Documents and Settings\taa\Application Data\lyx1.4.x directory was created again and everything seems to work.