jquery 1.3 and jquery.ui-1.6rc4 bug??

Hi,
I am using the Dialog Widget from UI, and I found this issue:
When I use jquery 1.3 and jquery.ui-1.6rc4 the dialog do not load
content via ajax,
but if I use jquery 1.2.6 it loads.
I need to know if it is a bug in the 1.3 version of jquery.
Regards