Map Merge Screenfreeze

Hi

I am using this plugin on a review site, http://www.greenwichmums.com and its plugin now not allowing me to merge existing maps. It used to a week or so ago!

How am I trying to create them do I hear you ask?

Well I go into the create map wizard through the button on the new page screen. Click 'advanced' which then gives me the 'Merge' button.

I then highlight the maps I want to group, hit 'Merge' and get my screen frozen. I have attached a screenshot for your info.

Can you help please!

Thanks

James.