This is how I solved the cron issue:

1. Via PhpMyAdmin, I looked in the semaphore table and deleted row where `name = cron`
2. I ran "drush cron" via command line
3. I seen an error message that gave me a clue of the issue; this may be different for you, but for me a recently uninstalled module that was sharing a PHP library with an installed module was causing an error