Some skins cause problems with the PopUp Windows displayed in some of the OnyakTech modules that show black squares and other odd visuals.
These problems comes from the fact that you are using global CSS in your skin which interfere with other third-party controls like ours (and any other control that uses CSS in its skins). In this particular case, the problem comes from the style you have for A and LI items. The images below show the problem and the causing CSS Style in the skins.
You can use FireBug to easily find and remove these unwanted (and not necessary) styles from your skin. Click here for a video that shows how you can use FireBug to do this.
To fix this, edit your sites Skin CSS file and remove the following styles: