could not find block containing chunk 0x8483530

select *, lower(name) from student;
gives error: could not find block containing chunk 0x8483530

what does this error mean & what may be the cause?

template1=# \d student
Table "public.student"
Column | Type | Modifiers
--------+---------+-----------
name | devchar |
age | integer |

Regards
Vinay

--
Vinay Jain
Dissertation Project Trainee
DAKE Division
C-DAC Mumbai