The problem is that if you restore a sql server database on a different computer than the backup was created, you can have the problem that the usernames and permissions are somewhat lost.
Each username has an associated SID. So even though you might have a user named ‘Bill’ and the restore database might have a user named ‘Bill’, they will have different SIDs and so the permissions will not be applied to the correct user.
To fix this problem you can follow the following steps:
1) run this TSQL:
2) This will produce a table showing you Users that having issues.
3) run the following TSQL:
sp_change_users_login 'update_one', 'UserNameFromStep2Table','NameOfUserToUse'
In many cases the 2nd and 3rd parameters will be the same string.
More about this SP can be found here: http://doc.ddart.net/mssql/sql70/sp_ca-cz_4.htm