The bug with gen_subnetv4_max() on 32-bit systems effects quite a few disparate places, and sends PHP into a spin whenever it tries to iterate through to the (erroneously calculated) subnet max IP address 255.255.255.255.
It is fixed by commit: https://github.com/pfsense/pfsense/commit/e69a0cf3a216c8647a6def4eee41ab01319ce90f
This causes quite a few times of tracking down symptoms in the forum.
The latest case effected firewall_nat_edit.php when there are VIPs: https://forum.pfsense.org/index.php?topic=88912.msg491627#msg491627
On all 32-bit installs of pfSense 2.2-RELEASE it is "a good thing" ™ to also apply the change to /etc/inc/util.inc in the commit above.