The ALTGX MegaWizard Plug-In Manager generates a clearbox.exe error when configuring PLLs for Stratix IV GX

In the ALTGX MegaWizard Plug-In Manager, on the Modes page of the Reconfiguration Settings tab, if you turn on Enable Channel and Transmitter PLL reconfiguration and Use additional CMU/ATX Transmitter PLLs from outside the Transceiver block, set How many additional PLLs are used to 2 or 3, and then on the Main PLL page turn on Use central clock divider to drive the transmitter channels using X4/XN lines, clearbox.exe generates an error:

clearbox.exe has encountered a problem and needs to close. We are sorry for the inconvenience.

Before you turn on Use central clock divider to drive the transmitter channels using X4/XN lines, on the PLL 2 page, change What is the PLL logical reference index (used in reconfiguration) from 2 to 3.