Issue when I try to create a form

Hi,
I’m have trouble trying to create forms. The form items (below the form short-code)won’t show when I click on the title, so I can’t drag/drop them into my form… I tried to update Java but that didn’t help… Everything is up to date… I’m currently using Mozilla Firefox v29.0, I also tried with IE but nothing… That’s too bad because I thought it was e very useful tool when I first tried it (a few weeks ago it was working)… But I had some issues with my e-mails which are corrected now.
So if anyone has an answer to my problem ?

Thanks for reading all of this and for trying to help me.
I apologise if my English is not perfect, it’s not my mother-language.

https://wordpress.org/plugins/visual-form-builder/

_____________________________________________________

EDIT : Ok, so I tried to deactivate the last plug-ins installed and it worked, when I reactivated them, it was still working… So I don’t understand what was going wrong… But it’s solved (haha.. but for how long, we’ll see if it does it again…) !