Two sites one PC

I think you are doing everything wrong. You should just use 1 WP installation and ENABLE MULTI-SITE feature, and then you can open as many separate WP sites as you want! NO NEED TO INSTALL separate WORDPRESS installations.

Cannot upload themes. Error: “The uploaded file could not be moved to /var/www/wp-uploads/localhost/2011/10.”

From quick search of source for this error message, it is likely to be triggered by failed move_uploaded_file() function call, which is native PHP and not WordPress. Documentation says that it has some restrictions, related to safe_mode and open_basedir so that might be your issue. Since WP suppresses error output from this function with @ … Read more

Debug errors for “Destination directory for file streaming does not exist or is not writable”

Your problem seems to be related with a misconfiguration of the temporary directory in PHP which is used for uploads and need to be writable when the sever downloads a WordPress, plugin or theme package. If you can not configure it at PHP level, you can define it also in wp-config.php file: define(‘WP_TEMP_DIR’, ABSPATH . … Read more