black screen after installing "nvidia-settings"

[geni49]

LMD15 Mate
Mainboard: A7N8X-XE
Grafikkarte (AGP): MSI FX5500-D256
Monitor (CRT): EIZO FlexScan T57S

After installing "nvidia-settings" (silly I) the system boots, you even get the MINT splash-screen and then: BLACK SCREEN
Blindly you can enter User and Password the system is "ON" but you only see a black screen.
Before it worked perfectly!
(I know: never change a running system...)

Is there a way to to fix it without a new installation?

[trapperjohn]

First, [cntl][alt][f1] (press simultaneously) will drop you to a command prompt. From there, we can probably dig out.

When you installed nvidia-settings, do you recall running:
sudo nvidia-xconfig

Also, did you at anytime install the proprietary NVidia driver?