Fatal error, no idea what to do

Hi guys, been running this wordpress installation fine for well over a year, upgraded on time, etc. Then this morning this greets me when I try to access wp-admin:

Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 128 bytes) in /home/darkdiam/public_html/wp-admin/admin-functions.php on line 1367

I also cant see the index, it only loads up to a certain point but nothing at all shows.

I’m a very confused, no idea what to do, any help would be greatly appreciated!