Stop Watching Throws an Error after Upgrade to 4.2.x Due to Proxy Configuration
Symptoms
After an upgrade the message "The JIRA server was contacted but has returned an error response. We are unsure of the result of this operation" appears when a user attempts to stop watching a JIRA ticket.
Cause
JIRA is behind a proxy server that do not allow DELETE requests. In JIRA 4.2.x the watchers control was changed to use ajax, in other words no full page refresh is required any longer to add/remove yourself as a watcher. It's common practice to implementing adding as a PUT/POST request and removal as a DELETE request.
Workaround
Allow DELETE requests to go through your proxy server.