The default thread stack for Apache binary is 256Kb [1]
However, apr_thread_create() allows to use a different stack size
(apr_threadattr_stacksize_set).
The value used is stored in the global variable ap_thread_stacksize
which can be set in ThreadStackSize at httpd.conf
http://httpd.apache.org/docs/2.2/mod/mpm_common.html#threadstacksize
Can you confirm that increasing it fixes your problem?
It surprises me that Pierre recommended tweaking the PE header instead
of the config option.
[1] Here are the relevant fields for
httpd-2.2.17-win32-x86-openssl-0.9.8o.msi
40000 size of stack reserve
1000 size of stack commit
100000 size of heap reserve
1000 size of heap commit