Update - 11:42am EST - Thursday, April 21
The load/save problem has been fixed but we are still monitoring the situation closely. You should no longer experience a failure except in rare cases. If a project fails to save or load, simply try again in a few seconds unless you stop receiving success or failure messages within 60 seconds of trying to load/save (see screenshot for failure message - success message is similar but green.) In that case please reload the editor and try again.