In the 'pictures' tab of the entry editor, there are two ways to add a photo, either using the first upload form or the alternate upload form. Only the first upload form gives confirmation that a photo has been uploaded. I accidentally used the alternate form first, thought it didn't work then used the first upload form. When I published my entry I then had 2 of the same picture attached to the entry. When I went to edit the entry, I selected the picture tab then tried to click on the red ex on the duplicate picture to delete it. In Firefox 3.6.11 it didn't do anything. In Internet Explorer 7 I followed the same procedure and was given an alert window that asked whether I really wanted to navigate away from the page because I'd lose all changes. The options are 'ok' - navigate away from the page and 'cancel' - stay on the same page. Either choice leaves me on the same page with 2 copies of the same picture still attached to the entry.

Is this a known issue or is it a technical problem (either user error or otherwise)?

It isn't, I'll look into it. Thanks :)