bash: fork: Cannot allocate memory Apache

I have a server that is not a virtual machine, and has plenty of RAM (32GB) and its using less than 6, but I constantly get this error when running some programs.

root@DAL1-727]# free -m
bash: fork: Cannot allocate memory

if I then kill something benign (like an extra bash session I had open in screen) I can get it to let me do things:

[root@DAL1-727]# free -m
             total       used       free     shared    buffers     cached
Mem:         32067       5015      27052          0         55       1293
-/+ buffers/cache:       3666      28401
Swap:        16095          0      16095

I'm opening a lot of files and apache is probably the cause. I've tried setting my file limits higher, but this still happens.

ulimit -n 1048576

output of /etc/security/limits.conf

soft nproc 65535
hard nproc 65535
soft nofile 65535
hard nofile 65535
apache hard nofile 64000

What else could this be?