What I would suggest you do is first clear off all iPod related media from your device such as podcasts videos and music by selecting in iTunes not to sync it. Wait until it completes, restart your phone then resync your library back.
Well I don't have a definitive answer for you but everything I've read says it's related to either a bad install of a jailbroken app, a bad source, or accidentally deleting a certain file. So many variables, so I'm not sure where to go from here other than a restore.