WSOD on plugin activation

I have found that trying to install and activate plugins results in a white screen of death.

I get this error message:

Notice: wp_enqueue_script was called incorrectly. Scripts and styles should not be registered or enqueued until the wp_enqueue_scripts, admin_enqueue_scripts, or login_enqueue_scripts hooks. Please see Debugging in WordPress for more information. (This message was added in version 3.3.) in /home/sites/heteml/users182/t/e/f/tefjp25/web/tef/wp-includes/functions.php on line 3049

Notice: bp_setup_current_user was called incorrectly. The current user is being initialized without using $wp->init(). Please see Debugging in WordPress for more information. (This message was added in version 1.7.) in /home/sites/heteml/users182/t/e/f/tefjp25/web/tef/wp-includes/functions.php on line 3049

Notice: Constant WP_MEMORY_LIMIT already defined in /home/sites/heteml/users182/t/e/f/tefjp25/web/tef/wp-config.php on line 95

Warning: Cannot modify header information - headers already sent by (output started at /home/sites/heteml/users182/t/e/f/tefjp25/web/tef/wp-includes/functions.php:3049) in /home/sites/heteml/users182/t/e/f/tefjp25/web/tef/wp-includes/pluggable.php on line 896

Warning: Cannot modify header information - headers already sent by (output started at /home/sites/heteml/users182/t/e/f/tefjp25/web/tef/wp-includes/functions.php:3049) in /home/sites/heteml/users182/t/e/f/tefjp25/web/tef/wp-includes/pluggable.php on line 896

I have tried increasing the amount of memory available thorugh wpconfig, but that has not solved the issue.

Can someone help me make sense of these errors?

Thanks.