WPMUDEV plugin causing fatal memory error

I am getting this on the blackheath site Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 262142 bytes) in /var/www/vhosts/blackheathfencing.org.uk/httpdocs/wp/wp-includes/functions.php on line 364

and this on another site Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 308287 bytes) in /var/www/vhosts/londonregionfencing.org.uk/httpdocs/wp-includes/wp-db.php on line 1106

I have 57MB and 59MB free of 64Mb on these sites before trying to load this plugin! At moment it is refusing to load and I cannot update MarketPress. Hosting will not increase my memory limit but does it really need more than 10Mb to run?
Thanks