After installing CM9 on my Samsung Galaxy S+ (Plus) it gets stuck in the "SAMSUNG" screen whenever I restart, the very first screen (I guess). I have to press the Power button 10 seconds to restart when I come to that point. Did someone discover that kind of problem before, how can I solve the issue?
This is a common outcome for many possible problems. If you can get in to clockworkmod(or whatever custom recovery) try reflashing cm9. If that doesn't work try doing a factory reset from recovery (clear data/factory reset) and then reflashing cm9.
On the international SGS you always had to flash cm-roms twice (on first flash it sets up the partitions and on the second flash it finaly flashes the rom).
If you still can't boot, flash a stock ROM with Odin (I think it is Odin you use for flashing stock ROMs, since it is Samsung device, if not use whatever is recomended on XDA-developers under topic named something like "restoring a stock ROM"), and check that it boots that. After that install root, recovery and cm as before.
If you still can't get it to boot after that, let us know.