What games have a higher version of SD than 2.51.021?

Just this.

I believe:

Stronghold Update v1.2, and
The Italian Job

They all have the SafeDisc version 2.60.000 protection.

…which has blacklisted Daemon Tools (fixed), the guard module remains resident throughout game play, blacklists serialz on Internet gaming and probably other stuff we don’t know about yet.