What should I do with this: invalid page header in block ... ?

I suspect the error below is bad. - Running 8.0.1 on linux FC3 on AMD 64.

septicide=# delete from sp_log where sp_log_time < (now() - interval '7
days')::abstime;
DELETE 215822
septicide=# vacuum full analyze;
ERROR:  invalid page header in block 5991 of relation "sp_log_idx2"
septicide=# vacuum full analyze;
ERROR:  invalid page header in block 5991 of relation "sp_log_idx2"