It looks like the memory limit configuration you are hitting is from the php.ini setting. The current limit that you are bouncing off is 128MB, so while attempting to force the ini_set to 64M is valid, its still lower than the core configuration.
You can raise the memory setting in php.ini bu finding the following line;
memory_limit = 128M ; Maximum amount of memory a script may consume (128MB)
and changing it to
memory_limit = 196M ; Maximum amount of memory a script may consume (196MB)
You are only attempting to allocate another 4k of memory to the process, so you should not need to raise the limit too much.
Depending on the OS you are running, php.ini will be in /etc/php (RHEL) or /etc/php5 (Debian).