Was a new snapshot recently generated which included object changes? 

If so, and the snapshot is being applied then:

When subscribers are set up their either already have the schema and data, or the schema is pushed to them "yes, initialize the schema and data".  If when the subscription is set up the "yes, initialize the schema and data" is selected, then when new snapshots are applied, replication will try to drop the tables and recreate them.  I believe the problem is that the tables are dropped in no apparent order so parent tables could be dropped prior to the child tables; thereby causing the error you see.

To get around (I don't think you can without dropping the subscription):

• Drop the subscription
• drop the subscribers database
• (option 1)recreate the subscription with the "schema and data" option
• or
• (option 2)script the database on the subscriber and populate the data; then select "subscriber already has schema and data option"

Option 2 requires that you apply object changes to the subscriber manually.

I'm curious to see if others are using different techniques.  This is what we're doing and it seems to work.