JStree does not work properly with IE9. You can check it out on your demo page here . When trying internally, nodes cannot be collapsed / expanded, and the whole tree expands after loading. Some hint at this?
Found solution, change IE mode in the header (disable quirk mode):
<meta http-equiv="X-UA-Compatible" content="IE=edge"/>
It works for IE8 and IE9.
Add cache field:
'data': { "url": 'YourUrl', "data": { yourparameter}, "cache":false // <- added }