How to fix "the design unit was not found" in modelsim simulation?

hi,all

When i simulatｅ ＂PCI Express in Qsys Example Designs＂the example, i encountered the problem "error loading disign". I command this steps

1.download the pack "C4gx_pcie_Qsys_msgdma", and unpack the zip file.

2. use QSYS to open the project, modify the testbench to "Stand BFM" item and use verilog in generate tab.

3.generatre the files successfully.

4.change directory to "...\testbench\mentor"

5 type "do msim_setup.tcl" in modelsim command line.

6 command "ld_debug"

So the problem is appearing like this "Error: (vsim-3033) ./..//q_sys_tb/simulation/submodules/q_sys_altmemddr_0_phy_alt_mem_phy.v(2759): Instantiation of 'cycloneiii_ddio_out' failed. The design unit was not found."

Would anybody like to help me to fix the problem? Thanks