ServiceDesk does not show any advanced error details to the end user.
Look at the logs on ServiceDesk server (Logs folder under ServiceDesk install directory, C:\Program Files\Symantec\Workflow\Logs by default) from the same time for a more descriptive error message. In this particular case, look into sd.feeder.generalincident.log or sd.incidentmanagement.log
Alternatively, if you are working on ServiceDesk itself (that you seem to be doing based on the localhost address), I would recommend keeping Log Viewer open for the initial testing so you are able to keep an eye on any errors that may occur.