Breaking out of SLIM

I've installed SLIM as a light weight login manager but when it comes up the screen is blank and I can't work out how to get to a command prompt or break out... Any ideas?
Same as for any X session, CTRL-ALT-1 to 7. It's possible that doesn't work due to KMS, in which case you can only fix it by booting to single user mode and disabling SLiM. With SLiM turned off you can configure X properly by testing it with startx.
SLiM often need to be (carefully) configured before starting it otherwise you can easily end in this situation, or it working but not login into anything.

EDIT: its worth saying SLiM was abandoned upstream. :)