I recently updated my main machine to Ubuntu Jaunty 9.04 beta. The version of Dropbox I had with Intrepid stopped working after the update. To get it to work I performed the following steps in the terminal. (The following steps work on x86. For x86_64, the steps will be the same, but using different files):

1. Download and install Dropbox deb (32 or 64 bit) for Intrepid if you don't already have it running. (Note: Don't restart Nautilus)
https://www.getdropbox.com/downloading?os=lnx