The current version of Dropbox does not behave nicely on Fedora 14 – the Dropbox update daemon attempts to execute code from stack. This is prohibited by SELinux (and rightly so).
There is a workaround (taken from the Dropbox Support forum):
/usr/bin/execstack -c ~/.dropbox-dist/_ctypes.so
Let’s hope that Dropbox releases a proper fix for this problem soon.