Looks like massive load issues are causing usability problems and slowness for Dropbox users. Per TechCrunch:
Dropbox appears to be having significant issues as users have experienced slow speeds and/or inability to access their files for at least nine hours. Some users claim the site has been slow since Monday morning.
We sympathize with the Dropbox team – they are running a massive operation and have a great track record. Sooner or later, everyone has issues. That said, one of the beautiful things about the cloud is that it is easy to switch and offers a multitude of options. The ElephantDrive infrastructure has recently been upgraded and our online backup and cloud sync service (have you checked out the new Everywhere folder?) are running faster than ever before. If you’re having a challenge, try us out for free.