I have a similar problem. Only that using this code does not work even for the owner in some cases.
Some work and some don't. For some reason it seems to be linked to the age of the object which makes no sense to me. So I must be missing something also.
But somehow I doubt it because I hear a lot of others in-world talking about their particals not working right at times.
But I have not found anyone saying it's on a particular product and not on another. Until now it seemed to be random. I figured it was a fluke.
But one high selling product of mine in particular uses the code
llParticleSystem([ ]); as do many other prodcuts in SL. In my case it's supposed to shut off thrusters when a key is released. But this will no longer work for any reason on this particular product. No matter which copy of it I rez. It's the same for every owner of this product. The strange thing is that it worked just fine before the updates.
This same code is used in another object and it works just fine. So I'm sure when a Linden tests this code they get to see a working situation. And thus send a "problem resolved" email.
So it seems to me that there is a corruption issue going. But I have no idea.
What I do know is that this has costed me, and a few other people, a LOT in sales. And I find it strange that it is not been taken more seriously by any Lindens so far.
I have spoken to one linden about the issue and they claim to not have any reports of such matters. Yet I have filed quite a few myself and a few others I know have also.
Kinda makes me wonder whats really going on.
I know one thing, SL has become more and more difficult to do serious business in anymore.
I've shut down my vendors for that particular product and am counting how long it takes until the issue is resolved. Time is money.

Perhaps we should all start selling crap instead. Since that's the kind of platform we are given.
