iconv is messing up a spreadsheet generated by the Spreadsheet Excel Writer

Hi gang, I am generating a spreadsheet using the contents of a mysql table. I guess that there is something in the data that causes iconv used in the module's script to generate this error: *Notice*: iconv() [function.iconv <file:///C:/Documents%20and%20Settings/tgol/Local%20Settings/Temp/function.iconv>]: Detected an incomplete multibyte character in input string in */usr/local/share/pear/Spreadsheet/Excel/Writer/Worksheet.php* on line *1547* This causes the production of weird characters in a cell in the spreadsheet and after that cell everything is printed out of order. The data in the mysql table are filtered for non-printable character before the data import. I have tried to filter the data before writing them into the sheet but this behavior persists. Any ideas in what might be wrong? -- Thodoris