Your file upload settings in PHP are probably less than your old server. Ask your host if you can modify any of these:
* session.gc_maxlifetime
* max_input_time
* max_execution_time
* upload_max_filesize
* post_max_size
Are all the missing images (in the Media folder) displaying on the live site?
Could be as simple as a permissions issue on a specific folder for some of those “missing” images in the admin (I’m leaning this is not the case but worth checking).
I have re-duplicated the site to new directory in fear that some of my files hadnt copied across correctly the first time. Everyone seemed to appear ok from the back end with the new duplicated site. I could see all my images in the media library. I thought I had fixed it.
Then again I tried to upload a large image. After trying again to upload the large image 2500px x 2093px my wordpress started to play up again and I got the HTTP error. Then images appeared to be missing from the media library and even some of the user interface of my theme is missing (it was there before I tried to load the large image). So I’m not sure what it is doing when I try to load a big image but it definitely messing stuff up.
My permissions seem okay. And yes everything is appearing fine to the live site.
If the upload settings are the problem – would that be messing up other things when I try to upload images that are too big? I find it strange that the back end of the wordpress site changed / things disappeared when I tried to upload the large image.
I just tried to contact my hosting company (Melbourne IT) and they advised they cannot help me at all with what you suggested. They said everything looks ok on the server. They were very unhelpful!
I removed the image via my FTP and everything seemed to go back to normal. Very strange. I can load the image back up via FTP and but the wordpress CMS does not seem to recognise it.
So at this stage it looks like I cannot load up any large photos. At least I got my CMS looking back to normal 🙂