right click on the file "on the other side" and choose "Get Info". Check the Owner of the file. Odds are you are logged in as a different user. If that is not the case, then just adjust the permissions on the file (also in the Get Info window).
Logged
We are the music makers, and we are the dreamers of dreams. - Wonka
Depends what "rip my folder" means! You could also be trying to work in a parent folder which hasn't the permissions that you need. This can happen for example if the folder was created by a script (e.g. a PHP script). When creating a file or folder from a script it is a good idea to set permissions so that you can also access the file/folder as yourself as user.