For the past three days I have been battling my Dropbox. I have space in the Linux Lab at Skidmore, and I have Dropbox installed on those machines to allow effortless syncing of project files between my machines. It's worked wonderfully for the last year and a half, but this week it got horked and I was only now able to fix it.
The problem started with the face that the Linux Lab has a hard limit on the amount of data that a user may have in their home folder. Working on a project, I initiated a download of a folder that caused the Linux machine to hit its cap so it was no longer able to create new files or directories. This caused the Dropbox sync to never end. The Dropbox account in the Linux Lab shares folders with my main Dropbox account, and the shared folders which were being synced in the Linux Lab also began to sync on my MacBook. After realizing that the Linux Lab was causing the problem, I cleaned up my Linux account so that it was under the cap, but Dropbox on the MacBook continued to try and sync. After restarting sync, quitting Dropbox, and reinstalling; I finally unlinked the local installation from my account, backed up the local Dropbox directory, and deleted the eponymous folder. I logged in to the web interface and whacked the offending directories in all accounts. I re-linked my Dropbox, redownloaded all new directories, and then copied in any new files that hadn't synced.
In the future, I recommend pausing syncing anywhere that's unaffected, making a copy, cleaning things up using the web interface, and then starting sync all over.