See also Orca bug #430402, that is currently blocked by this problem.
http://bugzilla.gnome.org/show_bug.cgi?id=430402

Steps to reproduce:

1/ Start Orca
2/ Start OOo Writer
3/ Create a simple OOo Writer document containing:

The quick
brown
fox jumps over
the lazy dog

4/ Make sure Orca is set to do "Say All By" Sentence
   (There's a combo box on the bottom of the speech pane.
    See last patch to bug #400716).

5/ Use Control-Home to position the cursor at the beginning
   of the first line.

6/ Hit the + key on the numeric keypad.

7/ Instead of speaking "The quick", Orca speaks "The quic" for the
   first line. There is a similar problem for each of the other
   lines.

The call in textLines() in default.py to:

[string, startOffset, endOffset] = text.getTextAtOffset(
                offset, atspi.Accessibility.TEXT_BOUNDARY_SENTENCE_END)

returns a string of

"The quic"