At least, this happened to me when I tried playing Vi in a solo custom game twice.
Each time, the game caused massive lag, resulting in display drivers crashing, restarting, crashing, restarting, only to completely lock up my computer and forcing a hard restart.
The current version on Live does not do this.
Hey Amélie, did you play any games with other champions? In that case did you get the same issue?
Can you try to update your drivers?
If you still get the issue after updating, can you upload your dxdiag and r3d logs from a game where you got the issue?
Instuctions on how to get those logs here.
@Dogmatist: Can you try updating your video drivers, and then check to see if you're still experiencing issues?
For anyone else having this problem, I'd like to ask that you first check to make sure that you've got the most up-to-date drivers installed on your system (you can get more information on doing so here.) If you're still having problems after doing so, can I ask for your updated Dxdiag information? Thanks much!