cannot delete bug

Dear Friends,
I am not sure this due to my hardware problem or due to a bug in
the postgres 7.2.

kzdb=# select id from mytable where id=7224; id 
------7224
(1 row)

kzdb=# delete from mytable where id=7224;
ERROR:  Relation 41073353 does not exist
kzdb=#

My simple solution is to dump the table as text
then \copy back in the table again after dropping
the old table.  This had repeatly happend to me.
I guess there is something very wrong somewhere,
bug I don't know.

If any one has any experience please let me know.
Apprciate.