The difference between association and database retrieval is that association looks in memory as well as in the database. I would assume that for some reason you have a discrepancy between memory and association. Are you changing this association in another place?
I would suggest you test this by committing that entity before opening the page, and see if there still is a discrepancy. Another reason why this might happen is association storage, I'm not sure which way your association is stored, but if it's stored in a different object than the one you are saving, your memory will be out of sync.
For example: Entity A has a one-to-many relationship with entity B. The relationship will be stored in B, and if you don't comit B when changing that relationship, your memory will differ from your database.