Can't install app

Hi,

I was just trying to install Transmission, but when I drag the application into my applications folder from the disk image, it says it cant be moved because an item named transmission already exists, then when I press ok, it leaves a small file (192KB) with a large cross through the icon.

Any ideas as to why this is happening?

The same thing happens when I try to install bittorrent, but not with Tomato torrent. The only difference between bittorrent, transmission and tomato is that tomato uses as installer to install, the other two are just drag and drop into the applications folder to start using the app.

Thanks in advance

Tom