Go to the Dropbox site. There is an update Dropbox will install that fixes it. Saw this on my iMac but not my rMBP.
their "experimental" build, that i suppose is simply a BETA of the next version, is not really fixing my problem, i hope it does with yoursIm having lots of problems with Dropbox since a couple of days. Never-ending syncs, high energy usage, disappearing Finder icons. Its really not up to snuff, so it wouldnt surprise me if your issue is related to that as well. Just wait for the next update and hope that it gets better!
their "experimental" build, that i suppose is simply a BETA of the next version, is not really fixing my problem, i hope it does with yours