i would try a complete refresh by unistalling the pandora app and installing again. if you pandora-one a/c works fine on a desktop, then it has to be something wrong with your phone.
if you don't have a desktop client for pandora, you can try with this app as it supports both pandora free and one accounts:
http://pandorian.djnitehawk.com/
just tick the box where it says "Use Pandora One".
if it stutters on the desktop as well, you better contact pandora support.