Sound ok, no video

[Jofo]

Mac OS 2.6.8, Intel Core Duo, VLC media player Version 2.0.6 Twoflower (Intel 32bit).
I've used VLC for years with no problem, but now it doesn't work anymore.
With ANY FILE (.avi, .flv, .mp4, etc.) I can hear the sound, but not see the video (the screen is always white).
I have uninstalled and reinstalled various version 2.0.6 (32 bits, 32-64 bits etc.) of VLC from different sites with the same result.
Why? What can I do to fix the problem?

[fkuehne]

Please reset its preferences by clicking on the "Reset All" button in VLC's preferences panel and restarting it afterwards.

[Jofo]

I didn't understand why, but it worked.
Thank you very much!
What was the problem?