I've seen in mentioned quite a few times here that beads will last a long, long, long time. The only thing I have seen that even resembles, "beads going bad", has been an
increase in the humidity output. I've seen a few guys here say that their 65% beads are regulating at 70-ish percent after a while, but that really isn't too big a deal as that range is still acceptable (though not as a preference to some perhaps).
If they are a dark yellow color, the only thing I can think of is that perhaps they are clogged with something foreign such as PG solution or from using non distilled water (such as tap water). Did you happen to do that? If so, that is probably the root of your problem. I doubt that beads kept in good condition, even in the company of dried out cigars, would go "bad". Of course, this is all just my opinion and I could be totally wrong, I am no expert in chemistry, hell I really don't know much about it at all, but I'd be willing to bet that is what the problem is.
Email Viper, I'm sure he will be more than happy to give you some insight as to what could be ailing those beads. Personally, I'd just toss 'em and order new ones, considering how inexpensive they are.
*EDIT:
Well, you got me curious and I did a bit of searching and came up with these threads:
http://www.cigarpass.com/forumsipb/index.php?showtopic=53497&st=700&p=840650&hl=yellow%20beads&fromsearch=1&#entry840650
http://www.cigarpass.com/forumsipb/index.php?showtopic=47785&st=0&p=704830&hl=yellow%20beads&fromsearch=1&#entry704830
http://www.cigarpass.com/forumsipb/index.php?showtopic=32045&st=20&p=475375&hl=yellow%20beads&fromsearch=1&#entry475375
http://www.cigarpass.com/forumsipb/index.php?showtopic=18929&st=0&p=282742&hl=yellow%20beads&fromsearch=1&#entry282742
It doesn't look like the yellowing is a problem, aside from the fact that it doesn't look pretty. Do your beads smell? (Man, after reading the Bill Clinton thread, that made me laugh typing that) If so, toss 'em, though seeing as they aren't holding water anyways I guess that is probably what you will do regardless whether they smell or not. Looks like Viper gives the reason for the yellowing here:
Do you think that the cigars are creating this color change in the beads? If so, makes me glad I don't smoke 24/7, I don't want my teeth looking like that!
It is a combination of the oils and gases the cigars give off as they age and the oils from the spanish cedar that the humidor is made of.