Fatal Error after plugin activation.

Keep getting this message everytime I activate marketpress.

Fatal error: Out of memory (allocated 54001664) (tried to allocate 30720 bytes) in /public_html/wp-admin/includes/update.php on line 49

I have 512M of server RAM.

With 1.5G Burstable

Using wordpress 3.4.2

I only have all the newest versions of buddypress, cubepoints, cubepoints-buddypress, cubepoints login widget, adminbar customizer, adminbar minimizer and the custom community theme activated.

Please help I can’t resovle this issue.