Problems restoring tables using 7.4.2

I am trying to restore tables and associated large objects under 7.4.2.
I created a backup using

pg_dump -U admin -Ft -b aesop > db.tar

When I try to restore it using the following command:

pg_restore -c -d aesop -U admin < db.tar

I get the following message:

pg_restore: [archiver (db)] could not execute query: ERROR: trigger
"RI_ConstraintTrigger_17414" for table "vm_message" does not exist

This is not a trigger I know about or created. What is the problem, this
worked okay on 7.2.1 before I upgraded to 7.4.2.

Even tried the --disable-triggers option on pg_restore, but this had no
affect.

Chris