Warning: ini_set() [function.ini-set]: A session is active.

After running any drush command, I receive this warning:

Warning: ini_set() [function.ini-set]: A session is active. You cannot change the session module's ini settings at this time in drupal_environment_initialize() (line 521 of /home/grasmash/public_html/includes/bootstrap.inc).

I ignored it for a while because the primary commands that I was using (dl, status) were still working. However, my site has now started to display the same error, and is now giving me an "Access Denied" error when trying to log in.

I can't anything online about this error. Any help would be appreciated. Thanks!