I've downloaded this app several times and it keeps disappearing or when it does stay, I cannot open a new file. The downloaded file drops into the Download folder and appears on the Dock. I think that the problem happens when I copy it from the Downloads folder into the Applications folder. I'm new to System 10 macs (this is system 10.6.1 on a new MacBook) so it might just be my lack of experience with the OS.