Fatal error: Allowed memory size of 33554432 bytes exhausted

I’ve got this error before, and I know what to do, you go to wp-config.php and change the memory size. I’ve tried to change it again, then update to the 3.1.3 WordPress, but it didn’t allow me to. Any reasons why?

And this is the exact error I got:
Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 3097329 bytes) in /home/*/public_html/wp-includes/class-http.php on line 1426