Fatal error: Out of memory

We have more than 700 members and more than 20 thousand pages, I wonder what to do with this error by elgg

When ever I enable plugin, it gives this error

Fatal error: Out of memory (allocated 63700992) (tried to allocate 47 bytes) in /home/mtecuk/public_html/tuacl.com/community/engine/lib/database.php on line 270


I have increased the size in php.ini even to 128 MB but its not working, I never expected such big bugg from elgg, and there is no solid solution for this problem, please help me finding solution for it.