Unable to Preview PopUp and Display Conditions not loading

I recently reported a problem with the same title as this post. Support appeared to be able to create a new popup OK on my installation but I was unable to respond to the questions as I had to go to Bolivia and had no internet access now. I can't respond to the original thread so I am starting this one.

Although I can see and edit the test popup created by support the problem persists with both Preview and Display Conditions. This is using the latest version of the Firefox browser. Using the IE browser it works fine. I have tried clearing down the cache etc in Firefox but it doesn't correct the problem.

I could easily use IE but Firefox is my preferred browser so if you want me to try out anything to trace the problem please let me know.

Thanks
Robin