'uid' is a reserved word on Oracle (see http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14200/ap_keywd.htm)
Here is the problematic query in backuplib:
SELECT uif.shortname, uif.datatype, uid.data
FROM {$CFG->prefix}user_info_field uif,
{$CFG->prefix}user_info_data uid
WHERE uif.id = uid.fieldid
AND uid.userid = $user->id
A simple solution is to simply rename the uid alias to uidata. The attached patch does this.