My audible email alert sounds for incoming mail quit working, I tried all venues, can someone help me?

My audible email alerts quit working the other day for no reason, the alert system that lets you know when you have a new email. The alert rings and the new email appears at the bottom of the tray and then a yellow envelope appears and then a star appears on top of that envelope. All of this quit working and I have tried everything. I went into Yahoo Messenger and applied the alert again for a million times and it still doesn't work. I know the ringing alert sound is working because I can do it Manually and the ringing sound works fine, it's just Not Synchronized with the incoming emails.. Does anyone have any more suggestions? What happened to my email alerts?