Today, a quite strange joomla problem crossed my way: I had developped a template and when I finally had zipped it, I couldn't install it:
Warning: file_put_contents() failed to open stream: permission denied in /xxxxxx/htdocs/libraries/joomla/utilities/compat/php50x.php on line 66
Well, I checked the templateDetails.xml file but everything seemed ok. Perhaps I had a problem with my local development server? So I took another joomla 1.5 template which I had already installed successfully on a client's server for testing purposes. As supposed there was no problem installing that template on my "joomla optimized" dev server.
I gave google the next chance to find a solution but I didn't find anything useful about my joomla-template-upload-problem. It seemed that the bug was neither in the template nor in the server configuration.