Recently, something similar happened to me too. Best thing to do is use Ctrl-Alt-Delete and close the program there. After a few times the problem seem to go away.
I couldn't close sl either but after a few days of doing this, the problem went away.
As far as sending crash reports for sl. If I were to send one for every crash -and I imagine most people too- I'd spent two-thirds of my time filing crash reports instead of being inside sl.