ORA error: infinite loop when restoring courses!

We have made a course backup on a 1.7.1-mysql-windows-system and uploaded the zip file to our new 1.7.1-oracle-solaris-system!

We started the restore process and got some ora errors (we create different issues for them!) and an infinite loop when the system wants to create the gradebook (categories, preferences, letters) - please take a look at the screenshot...

We have found a solution, but we're not quite sure, if its raising other issues... (...we haven't noticed yet...):
At line 1198

//Process preferences
if ($preferencescount && $continue) {
if (!defined('RESTORE_SILENTLY'))

{ echo '<li>'.get_string('preferences','grades').'</li>'; }

$counter = 0;
while ($counter < $preferencescount) {
//Fetch recordset_size records in each iteration
$recs = get_records_select("backup_ids","table_name = 'grade_preferences' AND backup_code = '$restore->backup_unique_code'",
"old_id",
"old_id, old_id",
$counter,
$recordset_size);

change "old_id, old_id", to only one "old_id",

Do the same at lines 1252 and 1302...

Heres the better readable error message again:

Creating gradebook

• Preferences
  ORA-00960: In der SELECT-Liste ist eine nicht eindeutige Spalte

SELECT old_id, old_id FROM m_backup_ids WHERE table_name = 'grade_preferences' AND backup_code = '1177587671' ORDER BY old_id

ORA-00960: In der SELECT-Liste ist eine nicht eindeutige Spalte

SELECT old_id, old_id FROM m_backup_ids WHERE table_name = 'grade_preferences' AND backup_code = '1177587671' ORDER BY old_id

ORA-00960: In der SELECT-Liste ist eine nicht eindeutige Spalte

SELECT old_id, old_id FROM m_backup_ids WHERE table_name = 'grade_preferences' AND backup_code = '1177587671' ORDER BY old_id

ORA-00960: In der SELECT-Liste ist eine nicht eindeutige Spalte
.........