too many apache processes

[Jorem]

I have a problem on 2 new low load (only 1 testsite per server) Ubuntu 12.04 servers (Perfect Server Setup). After a few days I get a max clients error and after that Apache crashes.

My current settings:
<IfModule mpm_prefork_module>
StartServers 3
MinSpareServers 3
MaxSpareServers 10
MaxClients 150
MaxRequestsPerChild 3000
</IfModule>

When I have higher settings here Apache crashes after a day.

The rest of the system is fully responsive. After the crash I checked the running processes and I see a lot of "/usr/sbin/apache2 -k start" lines.

It looks like the processes are not closed/terminated and endless processes are created.

Can that be the cause for the Apache crash? What can I do about it?