You receive an error, "Unknown Error," in the application.
An error occurred which the application doesn't know how to handle. This usually represents a bug in the application and should never happen under normal circumstances. Someone gets to write their résumé.
Submit the error to PDQ.com for further investigation.
Use the "Submit this [error|issue] to PDQ support" link in the More Info window or the "Report this [error|issue] to PDQ" in the error window.