I've had this problem for about six months, but I haven't been able to find a solution.
When viewing documents with writer or presentation containing math symbols/fonts, some of the symbols are either replaced with question marks or just left blank. The integral symbol is an example.
I can post some documents or system output for example if that would be helpful. I recently upgraded to Natty x64 (with packaged LibreOffice), but I've had this issue with Maverick x64 & OpenOffice as well.
I've downloaded msttcorefonts and cleared my font cache. For what it's worth, I also did a clean install for Natty.
Thanks for any help!