Math formulas broken after upgrade [closed]

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Hi,
I installed LibreOffice 4.2.7.2 few days ago. I haven't used Math for about one year. I just didn't need it. Now probably after several LibreOffice upgrade (like 4.2.X) I opened Math document and I see documents totally broken. Instead of "+", "-", "<", ">" characters I see telephone characters, letter character and other strange characters.

I thought it is font problem, so I changed all fonts to Arial, but the problem is the same. See print-screen: https://i.imgur.com/cFlWrtN.png

Is this some bug or is there some setting I can influence this strange characters?

P.S. I can't upgrade to 4.3.X, because LibreOffice is totally crashing every few second. See: http://ask.libreoffice.org/en/questio...

Regards