Due to a problem in the Quartus® II software you may see this error message when the WEAK_PULL_UP_RESISTOR option is disabled in a project targeting Cyclone® IV devices.
Active Serial (AS) configuration pins have internal weak pull-up resistors that are always enabled, so setting the Weak-Pull-Up option to OFF should not result in this error message.
To workaround this, remove the following line from the Quartus Settings File (.qsf):
set_global_assignment -name WEAK_PULL_UP_RESISTOR OFF
This problem is scheduled to be fixed in a future version of the Quartus II software.