rsDataSourceNotFound error in SSRS 2005

As soon as a report is re-deployed a refresh of the report in the viewer shows the following error message:

An error has occurred during report processing. (rsProcessingAborted)

The data source 'xxx' cannot be found. (rsDataSourceNotFound)

This error occurs irrespective of electing to re-deploy or not re-deploy the datasource, and the only solution seems to be to close the report viewer down and restart it.

Under RS2000 any changes that were made to a report, would automatically be shown to the user if the report was refreshed, without having to close the browser/application down and restart it.

How do I get around this error?

Pl let me know if anyone has encountered this error?