Links Window Does Not Open Up Properly

In a recent Enfold upgrade, I noticed that the link window, which usually opens up when you want to link some text would open up behind the text box instead of on top.

I then noticed that the issue was corrected in a subsequent release, however, I seem to be experiencing that problem again on my website.

http://www.web4business.com.au

I have upgraded to Enfold version 2.8.1 and am running WordPress 3.9. I have cleared my cached files and also tested it on both Chrome and Firefox and the problem remains. This is what happens.

I open a text box
Highlight some text
Click on the link icon
The background outside the text box goes from dark grey to black
No link window is open.
When I click on save, the text box closes, but the link window is open there
If I select Add Link, it doesn’t work
The only option I have then is to close it

I have done over 20 websites using the Enfold theme and I experience the problem on some client websites but not others. Other than my own website, no one has been upgraded to the latest version of Enfold.

Your help would be greatly appreciated.

Many thanks
Ivana