could not read block 84253 of relation "tablename": Input/output error

Hi:

No way to access "tablename". Can I do something to recover? Is this a
hardware error?

PostgreSQL 7.4.5 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2
20020903 (Red Hat Linux 8.0 3.2-7)

Thanks in advance.
Ruben.