The "x" next to report names has been removed as many users were finding it was too easy to accidentally click and delete their reports. The delete button is now located in the details page for the report ("Actions" -> "Show Details" when on the report page, or click the "Details" link when you report source header in the left-side navigator like "Actual Hours" or "Projects" to go to the reports list). You can only delete a report if you are the owner of a report.
I hope this helps! Please let me know if you have any further questions.