As you’ve probably noticed, WordPress 3.9 is now out there…
As previously mentioned, the current release of UpdraftPlus (1.9) is fully compatible with WordPress 3.9. Because WordPress 3.9 brings in a new under-the-hood database engine, the Restore and Migrate functions in previous version of UpdraftPlus are not compatible with WordPress 3.9. (The Backup function is). So, if you need to restore your website on WordPress 3.9, then you should first update to UpdraftPlus 1.9 or later.
Having said that, we always recommend updating to the latest version of UpdraftPlus for everyone. It’s always the best UpdraftPlus we know of!
David Anderson (founder, lead developer, UpdraftPlus)