Description
In the Quartus® II software versions 10.0 and later, the ALTLVDS_RX MegaWizard™ Plug-In window size is fixed. If your monitor's vertical display resolution is not high enough, you cannot view the bottom portion of the window.
Resolution
To work around this problem, use a display resolution with a vertical height of at least 900 pixels.
This problem has been fixed beginning with the Quartus II software version 11.1.