Had Nokia Notification installed on my N97 for a week or so. Love the app, but after some time it causes the phone to crash and hang. Even a reboot does not resolve this. Only thing that fixed it was to uninstall the app. Something is not quite right with this app yet.
I have the same problem. My N97 has the latest firmware and as soon as I put Notifications on my home screen (has been installed for a few weeks, but not used), it either says something like "there was an error, content removed" or it goes straight to a black screen, repeatedly reloads the home screen, reboots the phone, freezes the phone, selects random apps then opens them and crashes, etc - total chaos!