If you disable the plugin and the problem is resolved, then the plugin is your issue. If not, then it's something else.
If the plugin is the issue, then you have to figure out why. It could be conflicting with your theme, other plugins, WordPress core (especially if it hasn't be updated in some time), or your server configuration.
Your site looks fine to me right now, btw. (Although I misread it as greatcddeals.com and thought you were selling music!)