widgets screen error (wp_load_alloptions)

Hi.

I am running a pretty big WPMU site.

On the widgets screen I am an unable to drag/drag widgets and open/close the sidebar elements, in fact all javascript on this page does not work.

On further inspection when looking in the source code, the page does not finish loading and cuts out half way.

I tried disabling all plugins but there was no change.

If I disable javascript, I am able to do a couple of things, but because all the page content hasn’t loaded, only a couple of my sidebars appear.

I turned on php errors, and in my source code of the widgets page, I got the following:

<b>Fatal error</b>: Allowed memory size of 83886080 bytes exhausted (tried to allocate 86 bytes) in <b>/home/mysite.co.uk/public_html/wp-includes/functions.php</b> on line <b>463</b><br />

that line belongs to the following function

function wp_load_alloptions() {
                global $wpdb;

                if ( false == defined( 'WP_INSTALLING' ) )
                                $alloptions = wp_cache_get( 'alloptions', 'options' );

                if ( !$alloptions ) {
                                $suppress = $wpdb->suppress_errors();
                                if ( !$alloptions_db = $wpdb->get_results( "SELECT option_name, option_value FROM $wpdb->options WHERE autoload = 'yes'" ) )
                                                $alloptions_db = $wpdb->get_results( "SELECT option_name, option_value FROM $wpdb->options" );
                                $wpdb->suppress_errors($suppress);
                                $alloptions = array();
                                foreach ( (array) $alloptions_db as $o )
                                                (line 463) $alloptions[$o->option_name] = $o->option_value;
                                if ( false == defined( 'WP_INSTALLING' ) )
                                                wp_cache_add( 'alloptions', $alloptions, 'options' );
                }
                return $alloptions;
}

Any ideas?

The chances of me being able to upgrade the site to a later version are very slim.