Image Upload Glitch

I created a new thread, then went back to edit it to add an image.  Instead of success I got this highly descriptive error message:

Clearly I have the ability to upload images, but apparently just not when editing the first post in a new thread.  I have been able to add pictures to response posts while editing them.

A known problem?

P.S., this was the image I tried to upload to that other thread, so clearly there's nothing wrong with the image:

-Noel