Your screenshot is not meaningful as you clipped it and it does not show what the result should be.
And your description
everything goes crazy
is not really better.
Is View > Gamut Warning on?
I Imagined that the screenshot was pretty self explanatory. The canvas should be blank, but whenever I create a document in a colour profile other than RGB, I get a purple and black mess.
I'll check if Gamut Warning is on now.
Try resetting the Photoshop preference file: Press Ctrl+Alt+Shift as you start Photoshop. Select "yes" when prompted.
If the Layers Panel had been visible it might have been clear.
Does turning off »Use Graphics Processor« in the Performance Preferences and restarting Photoshop have any bearing on the issue?
Thanks for your help guys! This seemed to fix the problem.