Why do my custom widgets break when I use standard widgets?

Environment:

Custom/Standard Widgets
Customer Portal (CP)

Resolution:

There may be a possible collision with custom widgets and standard widgets of the same name being referenced on a single page.  

You cannot have two different widgets referenced on a single page that have the same folder name for the widget (which means the two widgets have the same class name in the controller).

That is, if you copy a widget and use the same name for the custom widget and if the copied widget uses the custom controller, the class value in the custom controller matches the class name in the standard controller. In this situation, you cannot include the standard widget and the custom widget on the same page.

This tends to happen with custom composite widgets. For example, a custom composite widget references a custom widget such as "FormInput" or "FormSubmit". If that custom composite widget is put on a page that also uses the standard FormInput or FormSubmit, it will result in the case where the standard widget and a custom widget of the same name is referenced from a single page.