Hi @foxtango,
Your issue description is not complete, but in general there are 2 reasons for Dropbox application inability to open web browser. If you have headless install and not default web browser exists configured (or incompatible terminal type only available), the application need to authenticate your account and since cannot open compatible browser it fails. Some recent browsers configuration limited themself access to temporary resources. On other side Dropbox rely to open web browser only using such resources - application bug - known bug that doesn't accumulate any attention from Dropbox development (like many others bugs), unfortunately.
To solve the first issue (if it is), you need to login without X redirection that confuses Dropbox application (and forces it to try opening something nonexistent). The second issue can be woraround as wiping out your DISPLAY environment variable and start Dropbox application in this context (so no more tries to open web browser, but the URL will be printed out on the terminal - where you can open it successful).
By the way it's always good idea to use Dropbox package' tools (Dropbox control script) instead of running directly the daemon.
Hope this helps.
