Though I didn't have the problem you describe, I was less than impressed with Cumulus. They do have some remarkable features that no one else has, but if you don't need those features they fall behind quickly. If you do need those features, then there's really no alternative.
From your description, it sounds like you're not using any of those features. If you're running Windows, I'd recommend ThumbsPlus. If you're on a Mac their are less choices. Extensis Portfolio would be the primary one, but I had it crash randomly on me (though I was using the Windows version).
Though it's pretty old now, you can read my
opinion here.