Problems to see the structure of a table

Hi,

After having some problems with our database server (in the hardware not
with postgres), when we execute '\d my_table' from psql it displays:

ERROR:  No such function 'format_type' with the specified attributes

We cannot execute the \dT command neither because it displays same
error. Could the reason be that some of the System files (as pg_type ,
etc.) are corrupted ?

How can we fix this problem ?

Any help will we apreciated.

Thanks,

Gabi :-)