Cannot Use The Special Principle 'sa'

Ok, here's my issue... SQL 2005.

I have about 12 different databases, which about 4 of them are have no user mapped to it. Under the SA login, databases are mapped to the "dbo". The 4 I am having issues with have no user mapped. They are blank.

Here is where I am at... Security>Logins>sa>Login Properties>User Mapping

The columns are "Map", "Database", "User", and "Default Schema"

Here is an example of the correct Selection
Map=checked, Database=eDistribution, User=dbo, Default Schema=dbo


Now here is an example of a problem database
Map=unchecked, Database=FORMS, User=blank, Default Schema=blank

Here is the error when trying to add the "dbo" as a user

Any ideas?

TITLE: Microsoft SQL Server Management Studio
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Create failed for User 'sa'. (Microsoft.SqlServer.Smo)
For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=9.00.1399.00&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Create+User&LinkId=20476
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ADDITIONAL INFORMATION:
An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)
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Cannot use the special principal 'sa'. (Microsoft SQL Server, Error: 15405)
For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=09.00.1406&EvtSrc=MSSQLServer&EvtID=15405&LinkId=20476
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BUTTONS:
OK
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TITLE: Microsoft SQL Server Management Studio
------------------------------
Create failed for User 'dbo'. (Microsoft.SqlServer.Smo)
For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=9.00.1399.00&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Create+User&LinkId=20476
------------------------------
ADDITIONAL INFORMATION:
An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)
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User, group, or role 'dbo' already exists in the current database. (Microsoft SQL Server, Error: 15023)
For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=09.00.1406&EvtSrc=MSSQLServer&EvtID=15023&LinkId=20476
------------------------------
BUTTONS:
OK
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