This is weird, I agree with that! :(
Would you please be so kind and send me the list of all your plugins that you have installed? Also, try to disable all of them (except ours) and see if this changes anything. If it does, slowly, one by one, activate the rest. This will hopefully give us some insight of where the problem might be.
If it does not, I would really appreciate it if you could send me your admin credentials so we can have a closer look, if this is OK with you. Here's my email address: firstname.lastname@example.org
Let me know how it goes and if the above mentioned option is OK with you.