Cannot connect to Bumblebee daemon

Hi,

I am struggling with a problem since two months now, and I still can't find any relevant answer with google.

So I've installed Bumblebee and Primus by following this guide: Bumblebee on Debian

The problem is that even though I redo the installation and aptitude-purge countless times, I'm still stuck with this message:

Code:

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primus: fatal: failed to connect to Bumblebee daemon: File exists

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And it occurs whenever I use "optirun glxgears" or "primusrun glxgears". My tests showed that the problem is the same whether using the "nouveau" driver or the nvidia's proprietary driver (319.72).

My CPU is an i5 2430m (HD 3000), and my GPU is a GT 540m which are of course Optimus capable.