Fatal Error on Allowed Memory size

I receive this error or a simialr area when I type on the Wordpress sidebar in a couple of area such as the header. Fatal error: Allowed memory size of 41943040 bytes exhausted (tried to allocate 87 bytes) in /home/business901/public_html/wp-includes/cache.php on line 672 I upgrade to the paid Catch Box theme 4.4.2 and when I do a live preview I get this: Fatal error: Allowed memory size of 41943040 bytes exhausted (tried to allocate 72 bytes) in /home/business901/public_html/wp-includes/cache.php on line 672 The site is up and running. Should I update the theme, even if a live preview is not working?