Issue: I was attaching a restored content database using STSADM -o addcontent to a SharePoint 2007 web using the command below when I got the following error: Could not find stored procedure 'dbo.proc_SetDatabaseInformation'
Solution: I found that the error message relates to the configuration database and there are lots of articles talking about different version patching issues.
However the real issue seems to be the -assignnewdatabaseid parameter. It causes SharePoint to look for the procedure which it cant find if the versions are missmatched. If you can get away with not adding the -assignnewdatabaseid parameter you should find it will run ok