Natalie,
If you look at the stack trace it seems as if the problem is with the Database Manager not being available. Do you have the following line of code in your Global.asax.cs Application_Start() event handler method:
App = new AppWeb();
If not, you need to add it in...if so, I recommend setting a breakpoint on this line of code to see what's happening.
Regards,
Kevin McNeish
Eight-Time .NET MVP
VFP and iOS Author, Speaker & Trainer
Oak Leaf Enterprises, Inc.
Chief Architect, MM Framework
http://www.oakleafsd.com