Thanks for answer.
Card driver update (Catalyst 12.1 from 1/25/2012) is done. - E.g. PS7, PSE9, Corel Paint3, Inkscape, Artrage and other non-graphic progs DONĀ“T show this phenomenon. Its only Paint.net. See video (cursor.wmv, 4.2 MB)
http://www.virds.de/cursor.wmv