Changing of machine name affects Sql Server
If you ever need to change your machine name (either due to joining a new domain etc), you'll realise that your Sql Server instance doesn't work properly after the server reboots. The simple workaround is to run the following commands in your Query Analyzer
sp_dropserver 'old_name'
sp_addserver 'new_name', 'local', 'duplicate_ok'
If you have a SSRS instance which is also affected, simply re-run your Reporting Services configuration and
1) setup the Database connection again
2) re-create the encryption key
This works for Sql Server 2005.