Re-create the component from scratch in SOPC Builder v7.2 SP2. Make sure all the needed HDL source files are added in the HDL Files tab.
Explanation: New versions of Quartus (>v7.1) use a different approach for the SOPC Builder components - the component's HDL files are used from their respective folders instead of being copied into the main project folder when the SOPC is generated.
When you create the component in the newer SOPC builder version, a TCL script will be created instead of the old class.ptf. This TCL script adds the needed HDL files for the component into the current project, so the synthesizer is able to find them.
Also, pre-7.2SP2 versions of the SOPC component editor are a little buggy.