The problem was related to the removal of \r's from older text
revisions. For now we have a workaround in place; dumps from this point
on whould work properly.
Στις 20-04-2012, ημέρα Παρ, και ώρα 11:23 +0300, ο/η Ariel T. Glenn
I'm seeing some failures to retrieve certain
revision texts for wikis
now running MediaWiki 1.20wmf1. The problem is being investigated.