This points to there being no space left on the disk but a quick df -h confirms this isn't the issue. These errors mean that there is no available IPC (inter-process communication) resources in the system, such as semaphores or shared memory segments.

The following script fixes this:

ipcs -s | grep apache | perl -e 'while (<STDIN>) { @a=split(/\s+/); print `ipcrm sem $a[1]`}'

Then to check the existing semaphore value (200 below)

/sbin/sysctl -a | grep sem
kernel.sem = 200        32000   32      128

To increase do the following