Try going to another view and then switching back to list view. I noticed that it always disappeared a couple of seconds after opening the app, but always came back a couple of seconds later. Now it simply disappears and doesn't come back until I switch views. Noticed it after upgrading my 3G to 4.1.
I'm syncing my calendar to Google, and I have the same problem. I use the same workaround the other poster mentioned (switch to day view and then back to list). This only started once I upgraded to 4.1. I have an iPhone 4, FWIW.