This started yesterday when I was trying to upload some images to a Jira issue. Initially the images upload fine, but when I click on "Insert", the attachment fails with the following error:

We couldn't save your attachment
Reload the issue then try adding it again.
After attempting to reload the page, clear the cache, etc. I figured I would try logging out and logging back in. This made things worse. After putting in my password and clicking sign in, I get the following message:

Oops, you've made a malformed request.
Often clearing your browsers [sic] cache and restarting your browser will solve this problem. If that doesn't work, please contact support.
This becomes a big problem. I am now totally locked out of Jira. Reloading, clearing caches, etc, do not fix the issue. I even try logging in from a separate machine. No dice. Same error message.
Eventually I manage to find a workaround. I put in the wrong password. This pulls up a link to the password reset form. I follow that workflow, reset my password, and I'm logged in!
And then I try to login to my primary machine with the new password. Same error. I reset my password again, and I'm logged in on both machines.
Today, I tried to attach those images again.

I assume the two issues are related. I have no idea why. But I really need a fix here. I have to be able to upload design screenshots for my team or Jira is not much good to me. Hopefully my detailed accounting of the last day and half triggers some insights for someone here.