ASP.NET Website Administration (Exception when adding users)

Upon registering new users, I encountered this error upon saving.
An error was encountered. Please return to the previous page and try again.
The following message may help in diagnosing the problem:

Exception has been thrown by the target of an invocation. at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.Web.Administration.WebAdminMembershipProvider.CallWebAdminMembershipProviderHelperMethodOutParams(String methodName, Object[] parameters, Type[] paramTypes)

I already have a custom ASPNETDB in my database..and using this db in my
test program will cause the exception above.

The solution is to add the default ASPNETDB in my APP_DATA folder
and change my web config settings to this:

<add name="ApplicationServices" connectionString="data source=SERVERNAME;  
 Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;"   
 providerName="System.Data.SqlClient"/>  

Since my db is an sql dev edition... :)