It is an IE only problem, no other browser is "not recognising" advanced selectors whether they support them or not, and it not breaking out, it's breaking back into, regressing to their previous support which will just happen to aid the transition should they ever get around to any CSS3 support. I don't care about the specs to letter, they have always always been open to browser interpretation.. this is just a plea from a real world user to help them :)
The scripts don't always use W3C standards, at least not in the CSS1, 2, 3 sense, when it comes to selector parsing "rules" but like forward thinking browsers they pave the way and give us the opportunity to try and use more advanced CSS. That's exactly why they are the solution.
It's been known for an absolute age that early adoption and usage of future CSS is the key to proving a selector, or property's worth and aids in the writing or even rewriting of a specification. How could we use them consistently x-browser without these scripts? - It should not ever be the other way around, else we will get stuck in the 'sheep' mentality or the can't think, won't think, of all possibilities,(i.e. non-real world) scenario we might have been in before if it weren't for forward thinking browsers like Opera and then FF. Opera first and then FF, took the lead in CSS (with or without their browser specific extensions, before they got specified too ;)).