Hi,
It seems that the application is not able to make connection with your SQL Server (hope so its MS SQL Server 2005!).
Under the repository.properties make these changes
# Database configuration
db.schema.update=true
db.driver=com.microsoft.sqlserver.jdbc.SQLServerDriver
db.name=alfresco
db.url=jdbc:sqlserver://servername:1433
db.username=alfresco
db.password=alfresco
db.pool.initial=10
db.pool.max=20
Cheers,
Sujay Pillai