[Errno 11] Resource temporarily unavailable

Hi all,

I'm getting this message probably every day and it renders Zenoss useless. Login in works however then I get the dialog to send error info.
So I have to login on the machine, kill the processes and restart zenoss again.

This machine is only running Zenoss.
zenoss-4.2.5-2108.el6.x86_64

On a CentOS installation.

VM:
- 4VPU
- 8GB memory

There are only about 30 machines on each zenoss.

I already highered ulimits:
ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 62676
max locked memory (kbytes, -l) 128
max memory size (kbytes, -m) unlimited
open files (-n) 262144
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 32768
cpu time (seconds, -t) unlimited
max user processes (-u) 16384
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited

When the issue was present I didn't see high cpu usage or number of processes. Neither high memory usage.
The only thing that I could say is that user zenoss had a bit under 8000 open files(files/pipes).

I don't know what else can cause this issue. Any help here