Application Validation did not succeed. Unable to continue

Hi Experts
I have been working on this app for a while now, using the Publish option within VB 2005 to create the setup files and until now this has worked perfectly.
Environment is VB 2005, SQL 2005, Vista and I repeat until this morning, everything was great.
When I now compile (publish) my setup files creates an error:
Application Validation did not succeed. Unable to continue

I am pasting this from the details provided in the error message which is:

ERROR SUMMARY
      Below is a summary of the errors, details of these errors are listed later in the log.
      * Activation of D:\IDT\IDT.application resulted in exception. Following failure messages were detected:
            + File, IDT.exe.config, has a different computed hash than specified in manifest.

COMPONENT STORE TRANSACTION FAILURE SUMMARY
      No transaction error was detected.

WARNINGS
      There were no warnings during this operation.

OPERATION PROGRESS STATUS
      * [2007/08/10 06:04:35 PM] : Activation of D:\IDT\IDT.application has started.
      * [2007/08/10 06:04:36 PM] : Processing of deployment manifest has successfully completed.
      * [2007/08/10 06:04:36 PM] : Installation of the application has started.
      * [2007/08/10 06:04:36 PM] : Processing of application manifest has successfully completed.
      * [2007/08/10 06:04:52 PM] : Request of trust and detection of platform is complete.

ERROR DETAILS
      Following errors were detected during this operation.
      * [2007/08/10 06:04:54 PM] System.Deployment.Application.InvalidDeploymentException (HashValidation)
            - File, IDT.exe.config, has a different computed hash than specified in manifest.
            - Source: System.Deployment
            - Stack trace:
                  at System.Deployment.Application.ComponentVerifier.VerifyFileHash(String filePath, Hash hash)
                  at System.Deployment.Application.ComponentVerifier.VerifyFileHash(String filePath, HashCollection hashCollection)
                  at System.Deployment.Application.ComponentVerifier.FileComponent.Verify()
                  at System.Deployment.Application.ComponentVerifier.VerifyComponents()
                  at System.Deployment.Application.DownloadManager.DownloadDependencies(SubscriptionState subState, AssemblyManifest deployManifest, AssemblyManifest appManifest, Uri sourceUriBase, String targetDirectory, String group, IDownloadNotification notification, DownloadOptions options)
                  at System.Deployment.Application.ApplicationActivator.DownloadApplication(SubscriptionState subState, ActivationDescription actDesc, Int64 transactionId, TempDirectory& downloadTemp)
                  at System.Deployment.Application.ApplicationActivator.InstallApplication(SubscriptionState subState, ActivationDescription actDesc)
                  at System.Deployment.Application.ApplicationActivator.PerformDeploymentActivation(Uri activationUri, Boolean isShortcut)
                  at System.Deployment.Application.ApplicationActivator.ActivateDeploymentWorker(Object state)