During my work with MOSS 2007,i had some performance issues regarding the SQL Server instance services which is running the configuration and Data for MOSS sites.
I had closed this service bymistake and when i'm trying to open the central administration site or any site i got this message in the IR:
"Cannot connect to the configuration database."
To resolve this : go to your services and start this service:
"SQL Server (OFFICESERVERS)"
This Tip is enough to continue your work with your MOSS sites.
Hope this helps.