I’ve just spent about a week trying to fix memory problems on a site with over 14 plugins running in a VPS Linux host. Finally I resolved it. Tried everything above, php.ini limit at 200M, made WP files set at 64M, etc. nothing worked.
Host made two changes:
1. added a php.ini file in server root (above www):
[PHP]
memory_limit = 200M
This helped in general with plugins that activated ok but too many being used at once caused fatal memory errors, but I was getting closer! Next, trying to active two large plugins like wp e-commerce and simple:press forum would give this error:
Fatal error: Out of memory (allocated 20447232) (tried to allocate 1077921 bytes) in /home/whatsyou/public_html/wp-includes/http.php on line 1331
2. Here’s what host support did next to fix everything. They commented out two lines in the httpd config file. Here’e what they sent me:
Please try it again now, I went ahead and commented out a couple lines in httpd that are known to cause problems with wordpress under suPHP.
#RLimitMEM 294876501
#RLimitCPU 240
Hopefully this helps if you’ve tried everything else. Keep in mind, the host said the memory limits on the server (in the php.ini file) showed more than enough memory so they said it’s the core site files – it’s not. Luck for me, I finally got a support person who’d been down this road already with WordPress and knew just what to do.