I've installed Bumblebee with Ryan McQuen's crazybee.sh script, described here, and I'm actually able to startx successfully now (because Bumblebee uses the on-board Intel graphics by default), but when I invoke optirun to run a program with the Nvidia card, I get:
[ERROR]Cannot access secondary GPU Failed to initialize the NVIDIA kernel module
The "Turbo" light on the laptop, which indicates if the Nvidia card is on, turns on when I invoke optirun, which is good.
I've tried the solutions to this "Cannot access secondary GPU" problem on ArchWiki, but to no avail…
Also, my trackpad freezes upon logging into KDE, so I'm thinking this might involve an issue in xorg.conf.
I'm running slackware64-current with the 3.14.27 kernel.
There's a thread about the "failed to initialize kernel module" part of this issue here, but it's old, from 2004.