A few days ago DropBox developed a bug in what seems to be most Linux distros. I found out the hard way by having it hang at 99% like everyone else. I was doing a clean install of Ubuntu 12.04 when I got struck. There is a work around out there, but it looks like DropBox fixed the bug. Found this link on the DropBox forums a bit ago. The 64 bit version worked for me, haven't tested the 32 bit yet.