I am using the Wordpress juicebox plugin. I am having trouble with Juice box displaying on some browsers and it seem totally random.

I get the following error message on IE 8 and 9, and Chrome. But  other times it is okay. In Firefox, the gallery tried to load but I do not get a message.

Juicebox Error: Config XML file not found.

Here is an example page:

http://www.clientssite.co.uk/wp/aaa/

I have spend hours trying to sort this issue but with no luck. I have tried deactivating plugins, clearing browser caches regularly - everything that is advised on your support forum. Sometimes it works on one browser, but not another. Very frustrating

Is this a known issue with Juicebox? 

PS I have bought the pro version but I have resorted to the free version to see if I can get that working first.