How can I re-spec my abilities in The Witcher 2?

I've begrudged some of the choices I've made in regards to ability choices while progressing through the Witcher 2, and now that I've reached Act 3, I've heard rumors that some sort of "secret quest" will allow me to reassign all my abilities from scratch.

Are there any truths to these rumors? If so, how do I accomplish this?

Yes you can,"From a Bygone Era" will work,but it is completly messed quest.I completed it by pure coincidence.

Here are some links that might help with quest.

http://www.gamespot.com/pc/rpg/thewitcher2/show_msgs.php?topic_id=m-1-59197966&pid=975399

http://www.gog.com/en/forum/the_witcher_2/quest_from_a_bygone_era

Yes, the quest "From a Bygone Era" allows you to reassign your abilities in chapter 3. So, it is generally possible, but only very late in the game. I did the quest myself and it worked, so it is not just a rumor.

The quest is started when you find a mysterious note you can't read in the quest "Little Sisters". You must hold onto this note to the next chapter, don't sell it to Deathmold when he asks. In the third chapter you will find a strange guardian in the sewer, you'll have to find out more about this note to get the password.

This is how it started when doing Roche's path, I don't if it works exactly the same for Iorveth's path.