And nope, none of the solutions I found seemed to work. WAVs don't work. WAVs converted into XWMs don't work. Recording silent voices through the editor (as described http://www.creationkit.com/Bethesda_Tutorial_Dialogue) doesn't work. Having WAVs, XWMs and LIPs doesn't work. Changing WAV files into FUZ by simply changing the extension crashes the game. Using Select Sound option to use a silent sound does not display the subtitles, and goes too fast anyway.
The only thing I haven't tried yet is using actual, properly done FUZ files, but I have no flipping idea how to use the http://skyrim.nexusmods.com/mods/950 that is supposed to create them.
So, shortly saying, I need help to get those silent voices to FINALLY work. Please help? I would be thankful forever even for a single FUZ file with about 7 seconds of silence, if it at least WORKS...

Thank you very much, now I can actually work with dialogues, and retrieve original dialogue from inside those mysterious FUZ files!