JQuery UI implementation Problem

JQuery UI implementation Problem

Hi, i want to implementate JQuery UI on our FormServer. But everytime i get an error.

a.plugins[e].push is not a function

The error comes from the jquery-ui-1.8.1.custom.min.js i renamed it in jquery2.js

The other File jquery-1.4.2.min.js i renamed it in jquery1.js works well

i can make a $('#test'); in firebug an get the right response.

Can you help me please? I really want to use the nice Functions of JQuery UI in our FormServer