Hi afennani,
This should be an old bug, can you download the latest version and try again?
latest version download url: http://ajaxuploader.com/download/Ajax-Uploader.zip
If you still get the same problem with the latest version, please create an example page which can reproduce this issue and send it to Kenneth@CuteSoft.net. I will check it and get back to you as soon as possible.
Regards,
Ken