I have migrated from 7.2.3 CentOS5 to CentOS 6.4 8.0.3 and all went very well.
The only issue is following:

=> I can't open spreadsheets created into zimbra (not the uploaded ones).

I got a blank page.
What I miss? I have read Zimbra 8 Release notes but I have not found anything related.
I have mailed it as an attach and saved the attached file, it is an xml file.
Can I convert it to Libreoffice format?

thnx for help