On a fresh Confluence 4.0.4 installation with SQL Server as database, we found the two constraints

• cp_unique_group (cps_id, cp_type, groupname)
• cp_unique_user (cps_id, cp_type, username)

On SQL Server (not Postgres, not MySQL), this prevents the user to add more than 1 page restriction of the same type (view or edit) on the same page.
Further we failed to import a space export, which was created on a MySQL Confluence 4.0.3 installation, because of this constraint.

It seems, that you are re-introducing the same bug again, that should have been fixed under

• CONF-22374
• CONF-23040

Since we figured out the workaround, which is also describe under CONF-22374, everything works fine.

Please make sure, that this bug is permanently fixed and keep it in your regression tests.