Rails - Aug 2006 - mysterious ''duplicate entry'' database error when building table

hi,

i tried posting this yesterday, but i never saw my message make it to the list
so i suspect something went awry.. 

my rails app has some ''sync'' code where it connects to a
remote db, grabs the
records from a table, deletes all the records from a table which is a local
copy, and then rebuild the table with the records fetched on the remote db.. 

it boggles the mind how a duplicate entry error can come up when the source
database is confirmed to have no dups in it, the local table gets torn down
completely, and rebuilt from scratch. the error only comes up every once in a
while, so often the code runs fine.. here''s the code in question:

   begin   #rescue block in event remote db is unreachable
     homelinks = Syncinventorydesc.find(:all)  #fetch all records
   rescue
   end
	
   InventoryDescription.delete_all()   #drop all records from local table

   for link in homelinks     #for each record we fetched..
       locallink = InventoryDescription.new()

       locallink.inventory_id = link.inventory_id
       locallink.description_id = link.description_id
  
       locallink.save!       #insert into table
   end

since it was just a duplicate entry (no loss of data) i just wrapped that save
in a rescue block too. the mystery remains however.. what happened?

thanks for the assistance!
stuart