scattered text

What can be the reason for ubuntu font to suddenly and without any time pattern start showing errors?
You open a file that uses Ubuntu font in LO or OO (XP or Ubuntu) and one moment it's perfect and the other you are getting a heart attac, because everything is messed up. Letters suddenly are not in lines but some words are scattered through many lines of text. Each line ie started with each letter of words that previously has been showed correctly.
I.e.
Text like:
Lorem ipsum dolor sit amet, ex vix nibh dolor, ut posse paulo similique mea.
would become :
Lore
m

i
p
su
m
dolor sit
 amet
,

e
x

v
ix nibh do
lor, ut posse pau
lo similiqu
e m
e
a
.

There's no rule on when the error will occur. Sometimes reopening LO or OO helps, sometimes you have to restart the whole system.
And as you can see the file without error - it will be printed like that. When errors are visible they will be printed or exported to pdf.

Selecting the affected text and changing size sometimes helps. Changing font helps always. But it's not an option when you want to use ubuntu font.