Do you have a ton of messages/threads you haven't deleted? Because if so, then that might be a contributing factor into not being able to use it properly.
I deleted all of my messages, it's still running slow and YouTube videos still don't play correctly. Is there an update I can run or can I take it into Verizon and just say "Make it better!"
Have you tried running an app killer? Try rebooting the phone, smart phones are computers and just like computers need to be rebooted once in a while. If neither of those work, its possible an app that you have is causing the problem, you can try doing a factory reset and then load the apps one by one, leaving a hour+ inbetween apps, to see which app is causing the problem.
Of course it could just be an OS glitch and the factory reset will fix it.