I've been a user and fan of LastPass for years. So long in fact, that I've apparently been overlooking a few settings that LastPass has introduced lately. Specifically, I've neglected to update my Password Iterations value.
You'll notice right away that the red text is floating the suggestion to you to raise the iterations used to create your master encryption key. If you're into light cryptology, click the More link to learn about how LastPass uses SHA-256 and PBKDF2. Otherwise, simply update the field above to 5000 and click the Increase Iterations button. You'll need to re-enter your password to start the key generation process.
If you're using Firefox, here's what you'll see:
Just login again (your password hasn't changed as a result of this process), and you're done!
It's important to keep in mind that, when you're an early adopter, it's easy to miss out on new features or capabilities that are introduced but are not retroactively applied to your account.