Screen is not cleaned properly

I have created small egine that put the results of the RawInput on the screen. I am using my own font texture. While I am not moving the mouse it is OK, the text moves and screen is cleaned. When I am starting to move it, see the attached video files from here
http://sharpdx.googl...Y:1335867800863
http://sharpdx.googl...M:1335867800863