They've just released an update v 5.0.1 - that fixed the issue for me. Go download & try it.
Yep - that's the only thing that worked for me too. Version 5.0 is simply a disaster. To revert back, you need to have the old version on iTunes. Make sure that you delete the new version from the iPad first, and then connect to sync with iTunes. Once the initial sync is complete, go to the apps tab, find Penultimate and then select Install. Click on apply - this will ensure the old version is synced back to the iPad.