Yahoo messenger

Hey all,
Two days ago, out of the blue, Yahoo Messenger stopped informing me of incoming messages. I usually receive a notfication box with that yodel jingle. The next morning, I decided to install the new Beta version 8.0. However, I still don't receive email notifications. I checked my preferences about 6 times and it says "Enable All Sounds and Alerts". I then uninstalled 8.0 and reverted back to 7.5. I still have this problem. I wrote Yahoo and that's a joke. They keep writing me emails telling me to stop using Messenger 5.6.

Help!