Hi Dani,
Thanks for the response.
As I have fixed all the problem image files there are no errors to see at the moment. I have added the strtolower() fix to the ulpoad.php file as you mentioned in the other thread, however I will revert to the original file and try uploading an image with an uppercase extensions and see what happens.
Both upper and lower case file extensions were working fine on my local Apache server so perhaps it's a setting on the other web server?