Hello again hassan,
Ok, I've found a way around this. In order to change the look of the text for the RadButtonElements that are in the QuickAccessToolbar under Windows7Theme you need to change the TextRenderingHint.
.RadButtonElement1.TextRenderingHint = Drawing.Text.TextRenderingHint.AntiAlias
I hope that helps, but let me know if yuo need more information