I have used Envy and it's an impressive bit of software. It installs the nvidia driver and there is some kind of problem with that on my system. I have found that I can continue by editing the xorg.conf file and replacing the nvidia driver with the nv driver.
The time I looked at this piece of software it tries to install the nv drivers as debian package. I tried the same for me before but later I thought that
nvidia-installer --uninstall
worked good enough in most cases. When a NV driver does not load, then usually the kernel module did not compile or the restricted drivers are active (on Ubuntu) and provide another kernel module. I am usually a bit radical when this happens and just delete every package with restricted in the name and use my own script *g*