Fatal error, after upgrading wordpress

I am getting this error after many of them. I’ve solved them all by saving and deleting all of my plugins. Only this error is remaining when I try to log in.

Fatal error: Allowed memory size of 262144 bytes exhausted (tried to allocate 77824 bytes) in /home/itechzone/itechzone.net/wp-admin/includes/dashboard.php on line 551

I really don’t know what else I should do. Please give me a hand here..

Thanks,
Costea.