I am not sure if I would follow Fdgsfg's suggestion as I feel that talents are not about knowing how to do something. They are about being able to do things rather than knowing how to do them. The things that a character knows I think are reflected by the Skills rather than the Talents.
Technically, you still have to learn the techniques, or you'd be able to do anything any Talent ever can by simply hitting the prerequisite if we would define it as being "able" to do something... I know, semantics, feel free to ignore them
So for example my character has the Dual Strike talent which has a prerequisite of Agility 40. If by getting Palsy I had rolled a 3 or more I would have agility less than 40. The description of Palsy says:
"The character suffers from numerous minor tics, shakes and tremors with no medical cause. Reduce his Agility by 1d10".
I think that it would be fair to say that after such a result the character is no longer fit enough to use Dual Strike.
A Problem coming with the abstractions of RPGs: Would a 3 Point loss in Agility really qualify for being an Argument? I'm assuming that'd be a fall from 42 to 39, meaning a total loss of Agility of some 10%. Now, speaking of Personal Experience, I lost probably far more then 10% of my physical capabilities compared to when I did Martial Arts... I can still perform a few of the tricks though, in game-terms I'd have probably lost the right to have the Talent unarmed Warrior, but I might just still have it.
TL/DR: I do see the necessity for abstraction when it comes to RPGs, but ultimately, there's going to be a lot of ad-hoc decisions to make the game more fun/fluid/whatever. Just my personal opinion though.
Also I would prefer in my GM ruled a clear "yes" or "no" in general so that we do not have to argue over this each time on an ad-hoc basis.
Foolish player, one does not "Argue" with a GM, one gives praise to this divine being in order to calm it's anger and appease it so it will be benevolent!
I can see your desire to have something solid you can count on in this case, but I'd probably suggest "assume you'll lose the talent, see how the GM thinks about this special case anyway". Worst case, you lose the talent, best case, you keep it.
Also, I should totally head to bed, I think I start making no sense.