I think vga=none is not a valid kernel parameter...
Testing this parameter will bring up an error.
I don't think that my problem is a result of the vga-value given through the kernel-parameter. Starting with vga=normal has the same result if shutting down (that is a hanging pc with weird things on the screen) as vga=0x314 (was the std. value).
I now will change the nVidia graphics driver back to 4191, so that I can shutdown my PC... without pressing the reset-button ;-)
If I can test something else, please write!
Thanx a lot,