Creating a relationship

I am very new to SQL Server and to S.S. 2005. I am trying to create a relationship using a database diagram. I keep getting this error:

'tblCASEMAST' table saved successfully
'tblCASECHRG' table
- Unable to create relationship 'FK_tblCASECHRG_tblCASEMAST'.
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_tblCASECHRG_tblCASEMAST". The conflict occurred in database "Criminal Records", table "dbo.tblCASEMAST", column 'CASENO'.

In tblCASEMAST, CASENO is nvarchar, length of 12 and a primary key

In tblCASECHRG, the column I am trying to link to is also nvarchar, length of 12

Any help is appreciated.

I found the solution. I had to delete the data, create the relationship and then import the data again.