Update 09:50 MT 23 Oct 2012 - We've rolled out our updates successfully, with no issues identified.

Update 09:45 MT 16 Oct 2012 - This issue actually began at 15:00 MT 15 Oct 2012, and was also the cause of some "504 bad gateway" errors for non-newsletter API calls.

Beginning at approximately 06:00 MT, 16 Oct 2012, Newsletter API users may have received errors while creating new Newsletters, new Recipient Lists, or scheduling Newsletters.

These errors are related to our upgrade to the new version of the Newsletter application. We have just rolled back the update, so you should stop receiving these errors as of 09:00 MT.

We will update this post when we roll the update out again.