SQL & PL/SQL

Hello,

I'm trying to exchange a table for a partition but I keep getting this error and don't know why. I'm using Oracle 10g in HPUX.
If I do it after creating the table/partition it succeeds but when I insert something it gives me this error. I tried to identify which columns aren't in the the correct order but the query below gives 0 results.
SELECT a.column_id "COLUMN_ID"
,a.table_name "TABLE_NAME"
,a.column_name
,a.data_type
,a.data_length
FROM user_tab_columns a
,user_tab_columns b
WHERE a.column_id(+) = b.column_id
AND (a.data_type != b.data_type OR a.data_length != b.data_length)
AND a.table_name = upper('LT_FUSE_CURR_SNAP_2007050416')
AND b.table_name = upper('lt_fuse_curr_snap_tmp')
UNION
SELECT b.column_id "COLUMN_ID"
,b.table_name "TABLE_NAME"
,b.column_name
,b.data_type
,b.data_length
FROM user_tab_columns a
,user_tab_columns b
WHERE b.column_id(+) = a.column_id
AND (a.data_type != b.data_type OR a.data_length != b.data_length)
AND a.table_name = upper('LT_FUSE_CURR_SNAP_2007050416')
AND b.table_name = upper('lt_fuse_curr_snap_tmp')
ORDER BY table_name
,column_id;

Any suggestions on why this happens?