Yes, the characters actually aren't the chinese ones. And, yes, MS Excel throws errors when I try to open the resulting file. I tried in two ways. Here go the steps I followed, the messages and the results:
By opening the .xlsx file in Excel 2007 I get the following message:
"Excel found unreadable content in 'report_file.xlsx'. Want to recover the contents of this workbook? If you trust the source of this workbook, click Yes."
By clicking 'Yes' I get the next message:
"The file is corrupt and can not be opened."
And then the file is not opened.
So I renamed the resulting file extension to .xls ("report_file.xls") and tried open in Excel 2007, getting the following message:
"The file you are trying to open, 'report_file.xls', is in a different format than specified by the file extension. Make sure the file is not corrupted and is from a trusted source before you open it. Want to open the file now?"
By clicking 'Yes' the file is opened and I see what actually isn't chinese chars, like the folowing, copy and pasted:
on cell A1:
on cell A2
on cell A3
on cell A17
and so on.
That is what actually happens.