The system could not log you on this could be because your user record or the business unit you belong to has been disabled
Microsoft Dynamics CRM is a wonderful tool. It can manage your sales very efficiently. You just need to emphasis on your budgets and other things. It will manage the rest without any problem. It is possible that you face some problems like given in the heading above. These are not very common problems. it can take more than expected time to fix these issues. I faced this problem while working with a client and there was nothing changed in the configuration and installation. MSCRM_DATABASE is used as the default database for the Microsoft Dynamics CRM installation.
Fixation is very easy but you need to know something about Microsoft SQL Server. Open the Microsoft SQL Server Management Studio and connect to the MSCRM_DATABASE. After connecting to Microsoft SQL Server Management Studio and opening the MSCRM_DATABASE database. Go to SystemUserBase table of the above listed database. Right click on the table and click to edit it. Once you have the table in edit mode, find the column with name IsDisabled. As soon as you find the column go to the respective user which is not able to login and check if the value against this user is 1. This clearly shows that the respective user is disabled and you need to enable it. Change the value from 1 to 0 and click on the RUN query of SQL Server. Once you are successfully done with changes, the respective user will be able to login to Microsoft Dynamics CRM.
This post is provided as is and I strongly assume that the user making changes have good idea about Microsoft SQL Server table editing. Please make sure there is a very recent backup of the above listed database. Better sage then sorry is my favorite approach to do this kind of hacks.