I'm pretty sure that the issue is the way it handles file names as no matter what i try and do to fix the issue it is pointing to line 124 ($URL = $fileObject->SetHeight($size)->URL;) of image_gallery\code\ImageGalleryManager.php.
I've also tried installing the newest versions of dataObjectManger, SWFuploader and image_gallery where it gave 2 blank pop up errors after installing, so I have reverted back to the semi-working version as before.
Cheers,
Rob