ERROR: XX001 (Critical and Urgent)

Hello All,
   
    Getting ERROR:  XX001: could not read block 17 of relation base/16386/2619: read only 0 of 8192 bytes, While vacuuming database
    Manual vacuuming and Auto vacuuming process constantly taking high CPU, not able to skip corrupted table for vacuuming and dump this message at regular interval.  fsync is off , From strace, found that semop call was in infinite loop.
     
    I have tried with making fsync on, Now manual vacuum process is taking high CPU, Strace unable to show any results (may be dead lock situation)
    and not any error / warning from postgres daemon

    Postgres Version : 8.4.3 (Migrated data from 8.4.1)

What can be issue ? Is it issue coming after database  table corruption, Can fsync on can prevent such (corruption) scenarios ?

Thanks,
Siddharth