Description
Due to a problem in the Quartus® II software version 12.1 and later, you may see this internal error if Rapid Recompile is enabled while using the Incremental Compilation flow.
Resolution
To work around this problem, ensure the Rapid Recompile option is disabled.
(Assignments > Settings > Incremental Compilation)
In the Quartus II software version 13.1 and later, this option has been removed and replaced with a seperate command which does not cause this internal error.