mails stuck in queue

hi there,i have a cron job set up for easydiscuss on my site and until recently mails got sent out without a problem. However at the moment mails are stuck in the queue and not getting sent out. When i check the mail activity i see recent mails stuck with the pending/clock icon. However when i try to select only the pending mails i get a message that there are no ending mails ....?
Could this be the result of the recent upgrade to a newer version that I did? Or is anything else going on ?