Last week, we announced the release of Jetpack 2.9 which introduced a related posts module and multisite support. Unfortunately, the release also contained a bug that prevented posts from being published if the Spelling and Grammar module was enabled. More specifically, if you have the module configured to automatically proofread posts and pages before they are published and you’re using the Text editor, the screen will become stuck after the publish button is pressed, preventing the post from being published.
Users have already filed multiple reports of the issue. The Jetpack team has already applied a patch to fix the problem. George Stephanis, who is part of the Jetpack development team told me the problem “stems from a change that accounted for WordPress 3.9’s pending bump to TinyMCE 4.0 and missed a conditional statement.“
Happiness engineer Brandon Kraft, mentioned in a support post the fix might be released later today if internal testing goes well.
We are looking to release a fix later today. In the meantime, for most people, switching to the Visual view before publishing works.
Until the update is released, I recommend disabling the spell checking module or use the visual editor before publishing the post as suggested by Brandon Kraft.