Hi Leoly,
Thanks for using my plugin and I apologize for the trouble you’re having. Problems like these are javascript plugins caused by the theme or a conflict with another plugin. To narrow it down is going to take a little troubleshooting.
Start by deactivating the other plugins you’re using, one by one, testing after each deactivation to find the plugin that may be causing the trouble.
If you’ve deactivated all other plugins, then the problem is most likely with your theme. You can confirm this by switching to a different theme, such as TwentyTen or TwentyTwelve.
If you can let me know how you make out, I can provide further assistance.
Also, if this is on a live site I can visit, please provide the linke as that would be very helpful.