Mantis#2591. Thank you kindly, Ruud Lathrop for a patch that:

This patch is two script that fixes a issue when adding more 
then 1 avatar to estateban/estatemanager list. It removes a 
key and adds a index to the tables.

OpenSim/Data/MSSQL/Resources/002_EstateStore.sql

@@ -0,0 +1,25 @@
+BEGIN TRANSACTION
+
+ALTER TABLE dbo.estate_managers DROP CONSTRAINT PK_estate_managers
+
+CREATE NONCLUSTERED INDEX IX_estate_managers ON dbo.estate_managers
+	(
+	EstateID
+	) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
+
+ALTER TABLE dbo.estate_groups DROP CONSTRAINT PK_estate_groups
+
+CREATE NONCLUSTERED INDEX IX_estate_groups ON dbo.estate_groups
+	(
+	EstateID
+	) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
+
+
+ALTER TABLE dbo.estate_users DROP CONSTRAINT PK_estate_users
+
+CREATE NONCLUSTERED INDEX IX_estate_users ON dbo.estate_users
+	(
+	EstateID
+	) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
+
+COMMIT

OpenSim/Data/MSSQL/Resources/003_EstateStore.sql

@@ -0,0 +1,25 @@
+BEGIN TRANSACTION
+
+CREATE TABLE dbo.Tmp_estateban
+	(
+	EstateID int NOT NULL,
+	bannedUUID varchar(36) NOT NULL,
+	bannedIp varchar(16) NULL,
+	bannedIpHostMask varchar(16) NULL,
+	bannedNameMask varchar(64) NULL
+	)  ON [PRIMARY]
+
+IF EXISTS(SELECT * FROM dbo.estateban)
+	 EXEC('INSERT INTO dbo.Tmp_estateban (EstateID, bannedUUID, bannedIp, bannedIpHostMask, bannedNameMask)
+		SELECT EstateID, bannedUUID, bannedIp, bannedIpHostMask, bannedNameMask FROM dbo.estateban')
+
+DROP TABLE dbo.estateban
+
+EXECUTE sp_rename N'dbo.Tmp_estateban', N'estateban', 'OBJECT' 
+
+CREATE NONCLUSTERED INDEX IX_estateban ON dbo.estateban
+	(
+	EstateID
+	) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
+
+COMMIT