One alternative is saving the IllustratorCS2 file with PDF compatibility "on." Sometimes Flexi can bring in the artwork successfully using the PDF import filter. Same solution applies for bringing similar files into CorelDRAW.
However, you're not really going hurt artwork quality by saving a copy of the file in legacy Illustrator 8 or even Illustrator 3 format. It will flatten layering in the document and perhaps break some AI-dependent "live" effects. But any of those kinds of effects should be flattened into actual editable vectors before being exported to another program in the first place.