I have just upgraded to IE9 RC (which i must add isnt too bad an attempt by microsoft, so far, they still have time to mess it up! Please dont comment below on how wonderful
I used IE9 on my laptop at my old job and it worked fine with jquery. And I was just listening in on the jquery dev meeting a couple of days ago and even on that they mentioned that only a couple of test cases fail. You may be having some other issue, maybe a security setting or something.