Strange memory limits

Hi, I have been chasing a problem for the last couple of days that has me stumped. I am running SLES9 on a POWER machine with around 30 gigs of ram. I want to run some analysis processes that will take up about 10 gigs of ram each. However, for some reason processes are running out of memory at the 3.7 gig mark on this machine. Actually, Python procs run out at 2.1 gigs and C programs start getting ENOMEM errors at 3.7 gigs. I don't have any per process memory limits set and this problem has me baffled. Any insight would be much appreciated. Thanks. --Narayan Newton