Question: In the newest release of Dropbox, the background of the icon is black (in the system tray). So no matter which theme you use, unless it's a black theme, the icon looks awful. Does anyone know the cause?

Answer: 
(Are you using nvidia drivers? from <http://crunchbang.org/forums/viewtopic.php?id=38154&p=2>, slightly updated)

This happens because nvidia driver overrode OpenGL library (libGL.so). This workaround works for me on kubuntu 14.04 [and linux mint 17].

1) close dropbox session

```
$ dropbox stop

```

2) find your nvidia system folder: in my systems it's /usr/lib/nvidia-331 (if you using another version of nvidia driver, for instance nvidia-340, your directory should be /usr/lib/nvidia-340). Take note of libGL.so.1 inside this folder

3) find dropbox system library. with dropbox 3.4.6 this is in the home directory.. the version number may change, and may have to be modified when you type it into the terminal

```
$ cd ~/.dropbox-dist/dropbox-lnx.x86_64-3.4.6/

```

4) backup your's dropbox OpenGL library:

```
$ mv libGL.so.1 libGL.so.1_backup

```

5) make symbolic link to nvidia's OpenGL library.:

```
$ ln -sf /usr/lib/nvidia-331/libGL.so.1 libGL.so.1

```

(so basically: ln -sf /usr/lib/nvidia-[VERSIONHERE]/libGL.so.1 ~/.dropbox-dist/[VERSIONHERE]/libGL.so.1

6) start up dropbox

```
$ dropbox start

```

Hopefully this helps, this worked for me. What it does is force dropbox to use the libGL installed on your system after nvidia overwrites it, by placing a symbolic link to the *nvidia* libGL in place of the one dropbox was installed with. After backing up the old dropbox libGL, of course.
Are you using `LC_NUMERIC=C`?

Open a terminal and try the following:

```
dropbox stop
export LC_NUMERIC=es_ES    (Put here your language)
dropbox start

```

That work for me.