Some versions of nv_check have major issues with some versions of the nVidia driver, and this is especially the case if your distro doesn't use devfs and you're using a version of nv_check that I screwed around with at all. You should be able to debug things manually, though.
First, check the output of lsmod for nvidia. You're using 4191, so the correct module name is nvidia.
If it shows up, you should be good to go.
If not, try an /sbin/modprobe nvidia as root. If that works, it will print no messages at all, and if it doesn't, it will. So if you see no messages, you should again be good to go. If you do see messages, post them here.
Once the module is loaded, try to startx. That should work. If not, post the X log.
To get the module to load automatically, there are a couple of different solutions. But make sure the module will load manually first.