Modelsim barfing on "oper_mux" in cycloneiv_hssi_atoms.v

If I had hair left, it would be gone by now. I cannot get Modelsim to properly load a design using a transceiver in a C4GX part. Now into day 3 of trying to do what should be a simple sim of the design but can't get the tool to work, at all. Can't find answer on forums or internet either. Sigh. I was using Q2 12 tools and in desperation just upgraded to 13.0 version, but problem persists. When trying to load the simulation, Modelsim consistently barfs on this:

** Error: (vsim-3033) C:/altera/13.0sp1/modelsim_ase/win32aloem/../altera/verilog/src/cycloneiv_hssi_atoms.v(14433): Instantiation of 'oper_mux' failed. The design unit was not found.

Whatever "oper_mux" is, it is called dozens of times in the cycloneiv_hssi_atoms.v file so I get this error dozens of times before Modelsim fails to load the design. I've pointed the simulator at all the libraries the transceiver megawizard indicates in Q2. Anybody have any ideas what magic setting I need to change, or obscure library I need to point the tool to in order to get the bloody thing to load the design?

I'd also like to put in a plug for the return of the native Altera simulator. In nearly 20 years of using that old tool, dating back to DOS days, I found it intuitive and very easy to use. It also played well with Quartus, i.e. was nicely integrated into the tool suite. With Modelsim, however, I've never NOT had a problem using it. Every single time I've used it has been problematic. What used to be simple and quick to accomplish with the old simulator now takes vastly more time with associated frustration/aggravation. It is just plain hard to use and counter-intuitive on so many levels.

Getting off my soapbox now. Any help is greatly, greatly appreciated. I'm stumped.