The report server cannot open a connection to the report server database - exception

We have SSRS and the database engine on the same box with the following configuration

Microsoft SQL Server Reporting Services Version 9.00.3042.00.
Microsoft Windows NT 5.2.3790 Service Pack 2

We are getting the following exception in the reportserverservice log file. All your help is appreciated.

ReportingServicesService!library!3!2/17/2010-03:40:19:: e ERROR: Throwing Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerDatabaseUnavailableException: The report server cannot open a connection to the report server database. A connection to the database is required for all requests and processing., ;
 Info: Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerDatabaseUnavailableException: The report server cannot open a connection to the report server database. A connection to the database is required for all requests and processing. ---> System.InvalidOperationException: Timeout expired.  The timeout period elapsed prior to obtaining a connection from the pool.  This may have occurred because all pooled connections were in use and max pool size was reached.
   at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
   at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
   at System.Data.SqlClient.SqlConnection.Open()
   at Microsoft.ReportingServices.Library.ConnectionManager.OpenConnection()
   --- End of inner exception stack trace ---

Thanks
Manoj