This has been a great and very useful plugin. However, I have a site where twice now the content has just disappeared from the multiple content blocks. It's happened on two different templates.
My best guess is that the content of the actual multiple content blocks never gets loaded when a page is loaded for editing. The user only edits the default wordpress content area, doesn't notice the multiple content block boxes are empty, updates the page, and then all multiple content blocks content are deleted because the blocks had no content?
Could this have something to do with the http requests issue mentioned in other posts? Unfortunately it appears to be an intermittent problem but one that has lots of potential for accidentally deleting site content.