same problem
I was having the what sounds like the same problem almost every day: a huge IO spike, and then the CPU is maxed out until I reboot. From watching top I could see that all the RAM and swap were consumed. OOM-killer unsuccessfully tries to save the system:
Out of Memory: Kill process 28567 (apache2) score 41314 and children.
It seems that Apache goes out of control creating new processes and eats up all the memory. A few days ago I lowered the MaxClients and KeepAliveTimeout options and it hasn't happened again since.
Hope this helps.
