By default smplayer calls 'mplayer -stop-xscreensaver', and mplayer crashes if it isn't built with X support. Reproducible: Always
What is your setup? Aren't you using X? Or are you using X without X use flag?
Fixed in 0.7.0 and 9999 ebuilds in gentoo-multimedia overlay.
+*smplayer-0.7.0 (04 Feb 2012) + + 04 Feb 2012; Johannes Huber <johu@gentoo.org> +smplayer-0.7.0.ebuild: + Version bump by Ben de Groot <yngwin@gmail.com>. This version fixes bug + #345653. Drop quit.patch, now applied upstream. Add mplayer[X], bug #377343.