Attack button held bug?

[seriph0]

So, I'm experiencing a bug where the character acts as if I'm holding down my attack button. For instance, when tapping the button with a melee weapon I perform a power attack. If I tap left hand I continue to block. With a bow out, it continues to hold an arrow nocked until I tap the button. I don't really understand what is going on here. I'm playing regular vanilla with no mods at all. I haven't messed around with any of the controls or settings. In case it matters, I'm using a 360 controller to play, but it is definitely not hanging on me as it works fine on my 360.