It looks like the same problem as Jeff had http://moodle.org/mod/forum/discuss.php?d=102124
( a filter problem I guess... )
On the other hand editor does change code in some cases - did you try to attach the orgnal.txt to editor in some particular activity or are you talking about adding a resource (web page) ? You may also disable editor from your user profile (When editing text -> Use standard web forms)