Try lowering the resolution, no fullscreen, 640x480. Run setup.exe as an administrator when using Vista or 7! If it still doesn't work, make sure all GRF files are in your AnimusRO folder: abdata.grf, rdata.grf, and sdata.grf. And the data.ini should contain:
[data]
0=abdata.grf
1=rdata.grf
2=sdata.grf
Maybe you accidentally removed or renamed one of those files yesterday.