[Plugin: WP Super Cache] Cannot delete or spam comments

I have a problem with WP-Super-Cache, it does not allow me to delete or spam comments, I can approve comments though.

While I try to delete or spam comments I keep getting this error

Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 774 bytes) in /var/www/techie-buzz.com/wp-content/plugins/wp-super-cache/wp-cache-phase2.php on line 273

No sure what is wrong here. Can u help?