I had the same issue with PP installs on 2 different webhosts, both of whom are using PHP5 as their primary php version. It seems that the default server configuration for PHP5 on most servers does not specify the session.save_path as "/tmp" - it simply has "no value", which will cause this exact problem.
You can contact your webhost and ask about the server configuration for the session save path to see if they are willing to fix it. If they aren't, there is something you can do to take care of this issue yourself:
I found a thread in this forum
that helped me resolve my issue on one of the webhosts - the solution was provided by GeoS.
Open up your FTP program and log into your server at the root of your account. At that level you should see several folders, one of which is public_html
. Check to see if there is a folder called tmp
at the same level as public_html
. If there is, you're okay; if not, create one.
Next, you need to open both index.php and admin/index.php in a plain-text editor (Programmer's Notepad
is a good one to use). You need to add the following line at the top of each of them (around line 45 in each of them, directly above error_reporting(0);
Make sure to save both files with UTF8 encoding and UNIX line endings.
Upload both to the appropriate places on your server, then try logging in to PP again and see if you can now upload an image. It should work now.
Also, when logging in to the admin section, make sure to check the box "Remember me" so that it will set a cookie on your computer.