Sharepoint database connection issue after upgrade to SQL Server 2008 R2

Note the following from Restore a farm by using SQL Server tools (Windows SharePoint Services 3.0):

You cannot use the Office SharePoint Server 2007 restore feature to restore the configuration database or the Central Administration content database. You cannot use the SQL Server 2005 backup and restore tools to restore your configuration database to a different farm or topology configuration.

In my experience, moving the configuration database doesn't work too well. I have had more success recreating it using this sort of process.

However, why don't you look into why the configuration database isn't accessible? It seems like overkill to move the database without troubleshooting the problem first. There should be more details about what the problem is in the ULS logs in the '12 Hive', or perhaps even in the event viewer.

The basic steps are:

1. Create a new web application in your new WSS server.
2. Follow the instructions in Move content databases between instances of SQL Server.

However you may not be able to perform all of the steps exactly as written if your previous server farm is not available. The main thing is that you get the most recent backup of the databases restored on your SQL Server, then follow these steps from the linked article:

13. In Central Administration, on the Application Management page, in the SharePoint Web Application Management section, click Content databases.

14. On the Manage Content Databases page, click Add a content database.

15. On the Add Content Database page, type the exact name of the transferred content database, and then click OK.

16. Repeat steps 14 and 15 for each database you are adding. Be sure that you select the correct Web application from the Web Application menu for each database.

I don't know your farm topology but if you are sharing the same SQL Server used for the dead server farm, make sure that the dead farm is completely powered off. You don't want two different SharePoint farms accessing the same data (especially if one is in an inconsistent state).