Problems With OpenOffice Calc

When i save an openoffice Calc Document in Microsoft Excel File all the Greek characters are appeared with the symbol “?”. The only solution is to save it to *.xls from the windows version of OO.org.
Can this problem be solved??

I want Also to notice that OpenOffice Calc Crushes too many times in some particular functions.

Thank you in advance.

Greek characters appear twice in the Unicode sequence, the first time without diacritics. It is possible that the Go-OO version supplied by openSUSE uses the second sequence which is not compatible with Excel. Alternatively, as the Sun Windows version works OK, there has been a regression in the filter supplied with the Go-OO version. I would put in a bug report.