Hi,
There's a similar topic, but nothing there works for me. Holding Space doesn't reveal any hidden buttons. I had files owned by root, but I changed the owner to my user (uid 1000) on the "source" laptop, and the problem persists (my uid on both laptops is 1000). There are not many files with spaces, and those that have them, they have them in the middle of a filename. I'm running Arch Linux, dropbox-176.4.5108. The sad thing is, there doesn't seem to be any logs to see what it's doing and what's the problem. I don't even know which files it can't download.