Go into Settings/Sounds & Display and make sure that Silent Mode isn't checked. If it is, uncheck it and set up the ringtone you want to sound when someone calls you. Hope this helps!
mine stopped ringing too...I don't have the silent mode selected and I have all the volumes up as high as they can go and have a ringtone selected...but when I try to call my android from my housephone, the icon pops up in the top section indicating the phone is silenced and it doesn't even vibrate. If I don't have my phone right in my eye sight I'm constantly missing calls that are coming in to me....
I figured it out!!!! whoop whoop whooop....hey Christie..turn off your WiFi....
go to the Homescreen on your Droid...select your menu, then settings...go to Wireless & networks...you'll probably see a green check next to WI-FI....unselect that...
then call your phone from your house phone or work phone or another cell phone...VOILA!!!!!
Thank you for posting a solution.