Error On Page: 'pageTracker' is undefined

Hi there,

My Drupal 6.9 works very well. When I need to add picture in my TinyMCE using IMCE, an Error on Page icon appeared in my IE browser. The details of the error is attached in the attachment below.

Effect: So far no problem. I can upload picture into my dir. But worried if something will happend in future.
Error on Page (The yellow icon with exclamation mark at left-bottom browser)
Error: 'pageTracker' is undefined

Thanks.