could not read block... how could I identify/fix

There was a hardware crash.
Since then INSERT to one table is failing with the following message:

ERROR: could not read block 11857 of relation base/16396/3720450: read
only 0 of 8192 bytes
ERROR: could not read block 11805 of relation base/16396/3720450: read
only 0 of 8192 bytes

Similar error was fixed by doing re-indexing or identifying corrupted data
by COPY command and remove the row etc.
However, the issue hasn't been resolved yet after taking the following
actions:

REINDEXed entire table. It was successful.
pg_dump was also successful then restore was successful.
COPY corrupted table to file was successful with no error.
Analyze was also successful with no error.

Do you think this should be the next step I might take?
Could you give me an advice of how I could identify corrupted error.

Version: "PostgreSQL 8.4.6 on i386-apple-darwin, compiled by GCC
i686-apple-darwin8-gcc-4.0.1 (GCC) 4.0.1 (Apple Computer, Inc. build 5370),
32-bit"

Thank you very much for your time in advance.

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Naoko