If I create with LibreOffice 3.4.4 a new .ods file and open it with excel 2010 excel tells me, that unreadable content has been found.
If I create a new file with LibreOffice 3.3.4, there is no problem!
Step by step:
1. create a new .ods file
2. save the file
3. close LO
4. open the .ods file with Excel 2010
5. Excel 2010: Excel found unreadable content in <filename>
6. same problem with .xlsx (created by LO)
I think, for the ods file type not the export of LibreOffice is wrong, but the import by Excel. The ods files open without any error in Gnumeric.
It is not worth to look, whether the export to ODF1.2 can be changed to allow opening in Excel without errors, because Excel drops all functions anyway and accepts only functions in its own namespace but not in the default open formula grammar.
The error in the xlsx file is already tracked in bug #fdo35062.
Created attachment 54042 [details]
Example created using LO 3.4.3. Will fail when opening with Excel 2010
I same seeing the same behavior in 3.4.3 that jens outlined.
The attached file will cause errors when opening with Excel 2010.
Google Docs opens this fine, so the theory that Excel does not support the standard may be valid. I did not see this problem in OOO-dev 220.127.116.1183 working with Excel 2010.
As jens describes, this behavior is not repeated in 3.3.4; it is seen in 3.4 only.
I followed the same steps as before, and I can interop between 3.3.4 and MS Excel 2010 with no errors.
This is not a bug. As Regina already mentioned Excel can't deal with ODF 1.2 and therefore is an Excel bug and not a Libreoffice bug. The output from Libreoffice 3-4 is standard conform.
I do not see whose fault it is as mattering much.
You may be complying strictly with ODF 1.2, but it is obvious that something in your output changed when going from version 3.3 to 3.4 that is causing Excel to choke.
Everyone knows that Microsoft is horrible at following standards, so I suspect you are correct, it's their bug.
But the important part here is that whatever you implemented in version 3.4 is breaking the interoperability with Excel. Find a workaround for this, such as the option of disabling it or saving into ODF version 1.1, which I did not see as an option.
For anyone facing this problem, there is an option to save as ODF 1.0/1.1 instead of 1.2 in OpenOffice 3.4/LibreOffice 3.5.
In Tools -> Options -> Load/Save -> General, choose the ODF format version.