Using 2 datasources, LDAP and SQL Server2005

Hi there,

I'm using Commerce Server 2007 and I wish to store a username and password

in ADAM while having the rest of the profile information stored in SQL
Server 
2005.

I have 2 datasources, one for LDAP that maps to the ADAM instance and one 
for SQL Server2005. In Adam, i'm using the user schema and I have mapped
the 
following fields

SAMAccountname
cn
accountstatus
givenName
Initials
sn

I then set the login to be a dual join field. When I try and create a new 
profile I get an exception saying that the underlying datastores cannot be

updated.

Has anyone any ideas?

Thanks

Davey