My app had the same issue and now it's fixed. It's not a free app, but it's free to try out. The issue was caused my WM2003 so there are a lot of alarm apps that are broken. We figured a way around the issue. Unfortunately our work around won't fix the built in alarm, but it does fix our app. Our app also can use MP3s/WMAs to sound off. If you guys are interested:
http://www.ATechware.com/