Postgres BackUp and Restore: ERROR: duplicate key violates unique constraint "pg_largeobject_loid_pn_index"

Hi,

I backup my database using the following command:

pg_dump.exe -f Backup.sql -U <username> -p <port> MYDB

Now,before restoring, i drop all my tables,indexes,foreign key
constraints.Then, i restore using the cmd below:

psql.exe -U <username> -p <port>-d MYDB -f Backup.sql

The above results in following exception and the data is not getting
restored:

ERROR: duplicate key violates unique constraint
"pg_largeobject_loid_pn_index"

What else do i need to drop/delete to completely reinitialize my
database ? Also, instead of dropping the tables,indexes,foreign key
constraints, if drop the database and recreate it, the above error is not
thrown.However, this approach is not an option for me due to some limitation
in my application.

Kindly help.

Thanks