Ora-01403 error

[osgood]

We created two users(A,B),sometimes we have to copy some data from one to the other.When I did it in Golden32.exe which was the third part software like PL/SQL. The ora-01403 error appeared. it said '' Can't find any data'', In fact there were a lot of data in that table ,But some tables can do like this .I used SQL sentences as following:

insert into B.table1 ( select * from A.table1 where [conditions])

I didn't know the reason, so I need some help from Oracle expert.
(The table's structure of A and B are the same )

[davey23uk]

break down the query into into subsequent parts, see which part is failing

i.e run the select on its own, see what it returns
make sur eyou have the proper permissions on the table as well