The Commonspot 5.1 upgrade includes some fixes for web browser conflicts when using Commonspot for authoring. Web browsers may retain cached versions of some of the upgraded javascript files in the upgrade, and so it's recommended that you clear the browser cache.
(from Paperthin's upgrade documentation)
For supported versions of Mozilla Firefox, you can access these options through Tools -> Clear Private Data or Tools -> Options -> Privacy. Review browser Help for more information.
For Microsoft Internet Explorer 8, click F12 -> Cache -> Clear Browser Cache or click Internet Options -> General ->Settings ->View Files -> Delete .js and .css files Note: For IE8 CTRL-R will not clear .js or .css files.
For Microsoft Internet Explorer 7, use CTRL-F5 or click Tools -> Internet Options. Under the General tab - Browsing History, click Delete. Review browser Help for more information.