I was going to give a long speech about how people need to READ before installing any new roms but considering the Hellfire thread doesn't list what works and what doesn't, I guess it's not entirely your fault :)
It's called "sleep of death" (SOD). Some ICS roms have problems with it and some don't. The same could be said about certain individual devices. You could boost your minimum CPU usage to 600Mhz or more, or try a different rom. Though, it should be noted that changing your CPU settings will affect battery life.
Change is free, but not freely given.