This is more of a wordpress problem:
You have a conflicting plugin or program installed on your site. Identifying the cause is recommended before attempting to fix anything. Last person who contact me with this type of problem had a shopping cart program installed that was causing it.
Once identified, I can help you fix it.
To begin, try this:
Maybe another plugin is conflicting.
Look on the Admin - Plugins - menu.
Temporarily Disable (not uninstall) all your other plugins.
Does it work now? If yes, Activate the plugins one by one to determine
which one conflicts. Which plugin was causing it?