Attaching a file results in an "The issue no longer exists".

I attempt to attach a file to an existing issue, and receive the following error, as demonstrated in the attached screenshot:

"Error instantiating webwork.multipart.parser.class: com.atlassian.jira.web.JiraMultipartRequestWrapper(original message: null)
The issue no longer exists."

The problem is consistently reproducible. When I attach a zipped version of the file, I have no such problem.

I was trying to attach the file SUP-559.tcpdump to the issue JSP-4997 in jira.atlassian.com.