Cannot have innodb puffer pool over 1GB in 5.1.30

[haro Ny]

As you can see I have set innodb_buffer_pool_size = 1600M in my.cnf but I am getting this error. This only happens when using MySQL 5.1.30 and does not occur in MySQL 5.0.67.

090125 17:57:24 InnoDB: Error: cannot allocate 1677737984 bytes of
InnoDB: memory with malloc! Total allocated memory
InnoDB: by InnoDB 39688152 bytes. Operating system errno: 12
InnoDB: Check if you should increase the swap file or
InnoDB: ulimits of your operating system.
InnoDB: On FreeBSD check you have compiled the OS with
InnoDB: a big enough maximum process size.
InnoDB: Note that in most 32-bit computers the process
InnoDB: memory space is limited to 2 GB or 4 GB.
InnoDB: We keep retrying the allocation for 60 seconds...
InnoDB: Fatal error: cannot allocate the memory for the buffer pool

I'm unsure if this is a bug, is there some sort of system configuration options that I must change or something to get it working above 1GB?

Thanks.