Due to a bug in the Quartus® II software version 14.0, you may see the Fitter error above when compiling the Seriallite III IP for Stratix® V devices using a data rate of 12.5Gbps and a transceiver reference clock frequency of 500MHz.
You can extract the following parameters from the 13.1.4 Seriallite III IP top-level RTL file and then transfer them to the 14.0 Seriallite III IP version.
reference_clock_frequency => "312.500000 MHz",
pll_ref_freq => "500.0 MHz",
data_rate => "12500.000000 Mbps"
Other data rates and transceiver REFCLK frequency combinations for the Seriallite III IP may also produce the Fitter error above. The same workaround can be applied by extracting the parameters from the 13.1.4 version and transferring them to the 14.0 Seriallite III IP version.
This problem has been fixed in Quartus® II software 14.1 and onwards.