Great, thanks for the input. Worked for me as well.
Mailchimp responded this morning the following.
Thanks for reaching out to us, I totally understand the concern here. I’ll be glad to help out wherever is possible.
We did a little more digging and discovered that this is actually a situation affecting certain feeds.
Our developers are looking into the issue related to feed validation, and why we’re unable to pull from it and at this time we do not have an estimated time frame of when we will be able to hear back from them. We will continue to investigate and push a resolution as soon as one becomes available. Once this becomes available, the update will be pushed to all accounts.
We’re always open to any questions you might have, and love helping our users. Please feel to inquire at any time for an update on the status of the fix. Additionally, if you have any more questions about this, or need help with something else, go ahead and reach back out to us.
In the meantime our usual RSS feed started working again without problems this afternoon again.
Thank you!