We have a web app using Andrew Valums ajax file uploader, if we kick off 5 - 10 image uploads at once, more often then not at least 2 or 3 will result in the same gd error "Corrupt JPEG data"
Warning: imagecreatefromjpeg() [function.imagecreatefromjpeg]:
gd-jpeg, libjpeg: recoverable error: Corrupt JPEG data:
47 extraneous bytes before marker 0xd9 in ....
However this did not happen on our old test server, or local development box's, only on our new production server.
The file size on the server is the same as the original on my local machine, so it completes the upload but I think the data is being corrupted by the server.
I can "fix" the broken files by deleting them and uploading again, or manually uploading via FTP
We had a shared host on Godaddy and just have started to have this issue on a new box (that I set up, so probably explains a lot :) CentOS 5.5+, Apache 2.2.3, PHP 5.2.10
You can see some example good and bad picture here. http://174.127.115.220/temp/pics.zip
When I BinDiffed them I see a consistent pattern the corruption is always 64 byte blocks, and while the distance between corrupted blocks is not constant the number 4356 comes up a lot.
I really think we can rule out the Internet as error checking and retransmission with TCP is pretty reliable, further there seems to be no difference between browser versions, or if I turn anti-virus and firewalls off.
So I'm picking configuration of Apache / PHP?
Well, i think the problem is jpeg-header data, and as far as i know there is nothing to do with it by PHP, i think the problem is your fileuploader, maybe there are some configuration for it that you are missing.