"Cron has been running for more than an hour and is most likely stuck". Try resetting the semaphore and deleting the "last run" timestamp from the database. (Note: deleting the "last run" timestamp will cause your Status report to indicate that cron has never run.) You can do so with this SQL...
DELETE FROM variable WHERE name="cron_semaphore";
DELETE FROM variable WHERE name="cron_last";
...or with this PHP in a custom module or script:
... or with drush:
drush vdel cron_semaphore
drush vdel cron_last