That is because Joomla doesn't have the writing rights after a fresh install for the affected folders.
Following folders should be write enabled for any extension you upload:
Then depending on if you upload a administrator(backend) or a user(frontend) extension the according folder needs to be write enabled. That could be:
In Unix/Linux systems the CLI command would be:
chmod -R 777 language
Where -R stands for recursive all subfolders and files of the folder "language".
Warning: Failed to move file! in Joomla Media ManagerWhen you try to upload a file in Joomla 1.5 via the Media Manager of the Backend you could run into a similar error as described above.
Warning: Failed to move file!
Error. Unable to upload file.
To solve this problem you need to write enable the images folder in the joomla base path. Not the media folder!
chmod -R 777 images