Problem in accessing reporting services web service, unable to set credentials I guess....

I am trying to access the Reporting Services Web Service, but i m not able to make it work. i tried with default credentials and network credentials

ReportingService

service =newReportingService();

service.Credentials =new System.Net.NetworkCredential("dbo","coreobject5","");

service.CreateSubscription(report, extSettings, description, eventType, matchData, parameters);

This is the exception i get

The current action cannot be completed because the user data source credentials that are required to execute this report are not stored in the report server database. --> The current action cannot be completed because the user data source credentials that are required to execute this report are not stored in the report server database.

Description:An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details:System.Web.Services.Protocols.SoapException: The current action cannot be completed because the user data source credentials that are required to execute this report are not stored in the report server database. --> The current action cannot be completed because the user data source credentials that are required to execute this report are not stored in the report server database.

Source Error:

Line 3382: [return: System.Xml.Serialization.XmlElementAttribute("SubscriptionID")]Line 3383: public string CreateSubscription(string Report, ExtensionSettings ExtensionSettings, string Description, string EventType, string MatchData, ParameterValue[] Parameters) {Line 3384: object[] results = this.Invoke("CreateSubscription", new object[] {Line 3385: Report,Line 3386: ExtensionSettings,

Tried to solve this and found that its the problem with the datasource I created for the report, tried to use 'sa' user in

data source->credentials->Use a specified user name and password, but did'nt worked.

One more thing i am able to accessGetExtensionSettings("Report Server Fileshare");API with

service.Credentials = System.Net.CredentialCache.DefaultCredentials;

Not able to find out what users to create in Report Server database or the database i am connecting to?

Will appreciate any kind of help.