Changing titles shouldn't deliver a penalty. At worst it will be dancing.
Thinking logically, I would assume you changed the title to try and pick up a higher search volume, with that in mind is it higher competition?
If it is the chances are you will eventually realign slightly Lower, therefore a little more work will be required to prop it up a little.
I changed titles and edited content on my main site last summer, and the long term effects have been great.