Hello, Christopher.
If this is the same problem I had (and discussed prior on this list), there is a bug in light-locker that seems to cause this behavior randomly even without hibernation. Consider switching from light-locker to xscreensaver; this resolved the problem for me.
Thing is, I never ever have any problem if I lock the screen but do not suspend, though. Anyhow, how do I get xfce to use xscreensaver as locking when suspending?
See also: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=913062
Killing light-locker gets me absolutely nowhere when it happens, I had already tried it :(
Andrea.