Fatal Error Message after activating Ubermenu

I just downloaded the plugin Ubermenu. It seemed to download successfully, however, when I activated the plugin I got the following error message:

Fatal error: Allowed memory size of 41943040 bytes exhausted (tried to allocate 30720 bytes) in /data/22/2/139/140/2791466/user/3071284/htdocs/wordpress1/wp-admin/includes/theme.php on line 48

Now I can’t access anything on my dashboard, I can’t even deactivate the plugin.

I am pretty much a newbie and I don’t understand what the message means, or how to correct this problem. Any help would be much appreciated. I have gone to the developers support, and submitted a support request, however, they only respond Monday – Friday, which means I cannot work on my website through the weekend.

Thanks.