NextGen Gallery – Images not displaying

I’m having an issue with the NextGen Gallery plugin.

When I upload images they upload fine and I can see them in the admin gallery but they don’t display in the gallery on the web. They don’t display at all in Chrome or Safari but show up intermittently in Firefox.

The only thing I’ve changed lately is to move my site to a dedicated IP.

I know very little about coding so am completely stuck! My site is very reliant on the galleries so not being able to upload new images is a bit of a disaster. Can anyone help?