Created Unassigned: autocompleteExtender in jquery tabs in Updatepanel display error [27534]

i put a autocompleteExtender in a jqueryui tab , and put the tab into an Updatepanel. It works. But when submit, the textbox which with the autocompleteExtender lost some alphabets.

i updated my ajaxcontroltoolkit and jquery and jqueryui to the newest version.But the problem still exists.