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Semaphore issues are generally indicated by "out of space on device" errors when there is still free space on the device. You can run 'ipcs -s|grep apache' to see the apache semaphores. If it looks like there are a lot, try clearing them out with 'ipcrm sem [semid]', or just run:

for i in `ipcs -s|grep apache|awk {'print $2'}`;do ipcrm sem $i;done;