Ive had this happen before. I dont really know what causes it, it just fixes itself usually. I did, however, find that at one point I had both of my devices with Google Now and they had different settings enabled and it was messing up what was shown. That was a while ago and I think the settings sync now. But you never know. If you have two devices, try that. Also, you can try to clear the data for the app and see if it fixes it.
Galaxy Nexus (Kitkat), HP TouchPad (Jelly Bean)
Palm Pre Plus
Everything before that doesn't matter.