My site's apache document index is configured as index.html index.php
I put a index.html which is a flash opening inside before entering the true content of the site.
Problem found when opening the browse server , it just shown the content of index.html instead of a file manager.
This problem doesn't appear on drupal 5.x
I post a bug report on maintainer of IMCE and reported that this is an issue of the application (a wysiwyg editor)
This is their response.
"This is not an IMCE bug. If you call imce using /?q=imce it will probably interpret this as /index.html?q=imce in your case.
The URL should explicitly be set as /index.php?q=imce, which should be an issue with the application(a wysiwyg editor) that opens IMCE."