Recently a particular folder in a site started coming up with blank php pages and the root cause being Segmentation fault after memory exhaustion. The subfolder contents would only come up after doing a restart of apache.
So something tried to access a region of memory that it did not have rights to. May be due to either bad RAM, or a code problem.
My first instinct was eAccelerator as I had done a recent php update and had not re-compiled it.
I still had the same issue the next day and bumped up the memory_limit from 16M to 32M in php.ini and from 32M to 64M in eaccelerator.ini .
