problem with NIOS simulation

It could be a bug in SOPC's automatic generation part... Check if you have any unusual configuration parameters, some signal or component names that contains characters that are not valid in VHDL, spaces in the path name for any file, or a VHDL entity that has the same name than a component in your SOPC design. (I got a few time some strange compilation errors because I used a component's top level entity name as the name of it's instantiation in the SOPC system, but in your case you seem to have kept the extra _0 added by SOPC builder)