Illegal connection found on I/O input buffer primitive

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Dear all, 

 I am using Quartus II 13.1 right now.  when I compile the project, can't pass the synthesis stage, quartus report the following error  Error (17044): Illegal connection found on I/O input buffer primitive camera_system:camera_0|camera_system_volatile_memory_subsystem:volatile_memory_subsystem|camera_system_volatile_memory_subsystem_ddr3_dram:ddr3_dram|camera_system_volatile_memory_subsystem_ddr3_dram_p0:p0|camera_system_volatile_memory_subsystem_ddr3_dram_p0_acv_hard_memphy:umemphy|camera_system_volatile_memory_subsystem_ddr3_dram_p0_acv_hard_io_pads:uio_pads|camera_system_volatile_memory_subsystem_ddr3_dram_p0_altdqdqs:dq_ddio[0].ubidir_dq_dqs|altdq_dqs2_acv_connect_to_hard_phy_cyclonev:altdq_dqs2_inst|strobe_in. Source IO camera_system:camera_0|camera_system_volatile_memory_subsystem:volatile_memory_subsystem|camera_system_volatile_memory_subsystem_ddr3_dram:ddr3_dram|camera_system_volatile_memory_subsystem_ddr3_dram_p0:p0|camera_system_volatile_memory_subsystem_ddr3_dram_p0_acv_hard_memphy:umemphy|camera_system_volatile_memory_subsystem_ddr3_dram_p0_acv_hard_io_pads:uio_pads|camera_system_volatile_memory_subsystem_ddr3_dram_p0_altdqdqs:dq_ddio[0].ubidir_dq_dqs|altdq_dqs2_acv_connect_to_hard_phy_cyclonev:altdq_dqs2_inst|obuf_os_0 also drives out to other destination than the buffer.  When I click this error, the .vs file pops out, it is not a coding grammar problem, and when I double click the error information that link me to a .vs which is not create for myself, it generate by quartus ip core. therefore, I don't really know how to solve this problem, actually no clue at all.  If anyone have experience this before, please give me shout, at least give me some hit, that will be awesome, thanks a lot in advanced.