I can't seem to post any images from any SE website. I get the error below. The uploader on their website seems to work fine as I uploaded the screen shot there.
Imgur was having storage issues again. We just got a mail assuring us that everything should be back up now.
The reason for that particular message is just that they're returning a 503 status code. And since that's not listed in their list of errors the API may return, you're getting our catch-all error message.
I'll add the 503 response to the list of responses that cause the "an error occured at imgur" message, that's more fitting in probably all cases.