Hmmm...not sure what causes the problem here.
The ODT plugin calls geshi like this (see file plugins/odt/page/renderer.php line 1146, function _highlight()):
// Use cahched geshi
$highlighted_code = p_xhtml_cached_geshi($text, $language, '');
I never examined what "cached" geshi means.
Maybe I will look a more deeper into this later but maybe this information already helps you.