Wysiwyg Internet Explorer looses changes on simple title

If you add a simple text in wysiwyg mode and switch it to "Title 1" style without adding anything else Internet Explorer 6 looses the content.

Steps to reproduce:

1/ Create a new empty document
2/ Switch to WYSIWYG mode WITHOUT adding any text in the Wiki mode
3/ Type "This is a test" without carriage return
4/ Select "This is a test"
5/ Choose style "Title 1"
6/ Save

The content is lost.