I recently upgraded a few of my Linux servers from Plesk 7.5 to 8.2. Everything seemed to be fine, however calls started coming in about PHP forms not uploading images correctly.
My team and I were troubleshooting this problem for a few days trying to narrow down the problem. We looked at folder permissions, script permissions, database connectivity, and almost anything else we could think of. Then we stumbled across the error message given by PHP (who would have thought to look at the error message?) that said function move_uploaded_file will not work in safe_mode.
Now looking at the PHP info the main php.ini was set with safe_mode off. However, I found that the httpd.conf for the individual domains on a Plesk managed server carries a declaration for PHP safe_mode, and it was turned on. Upon further investigation I found that in the Plesk interface for the domain there is a checkbox beside the PHP setting that allows safe_mode to be turned on and off.