If you try to insert a new issue without filling all three mandatory fields (category, title and description), obviously the issue can't be reported and appears a page telling you to push the "back" button of the browser to go back to fill missing fields.
The problem is that the button used to insert the new issue, at the bottom of the page, is disabled when pushed first time and so it's now impossible to push it again to report the issue, even if mandatory fields are correctly filled.
I've seen this using Firefox v3.5.