ERROR: heapgettup: failed ReadBuffer

I put 360000+ rows in a table , and now any select , update , analyze
... command fail.
the log shows "ERROR: heapgettup: failed ReadBuffer",
but any INSERT sql command success.

the table schema is

row | type | modifiers
---------------+-----------------------------+----------
test_id | integer | not null
snapshot | timestamp without time zone |
ip_client | inet |
ip_server | inet |
conn_time | integer |
response_time | integer |
response_head | character varying |
Check constraints:
"invalid_conn_time" CHECK (conn_time >= 0)
"invalid_resp_time" CHECK (response_time >= 0)

I didn't create any index,
any one know why or suggestion to save the un-readable database?

or anything I mis-configuration ??

Thanks for your help.

June-Yen