Damnit, I knew there was a reason I didn't do this before.

Install new drivers, reboot, enable SLI, all looks well.

Run keyclone, run clients 1-5. Entire computer freezes on loading client 2 (on 2nd monitor).
A single press of ctrl-alt-delete forces a reboot.

Reboot, try again, 1 client at a time. First client loads fine (on 2nd screen). Second client, keyclone gives an error about buffer overflow and closes.
Exit client 1, retry keyclone, client 1 loads fine, skip 2, client 3 loads fine, client 4 causes entire computer to crash like earlier.

Reboot, try again without keyclone. Client 1 causes entire computer to crash, this time giving me a blue screen with a stop: error.

Going to try without SLI, I'm thinking maybe it doesn't support any 3d stuff on a second monitor, since it gives me an option to choose which monitor to run 3d stuff on.

And my keyclone.ini file got reset somehow .