I've repeatedly tried troubleshooting with different ideas on the web but I don't see a case like this - after downloading the dmg Dropbox installer from the standard dropbox installation page, it opens up normally, and I double click on the Dropbox icon to install it, but then my Dropbox app is unresponsive and keeps hopping up and down in the dock and doesn't launch. I can't seem to figure out what is preventing it from launching - please let me know if there are any solutions!