In a recent project, we had a ticket filed for a seemingly broken Banner Rotator Widget. The admin console would allow the creation of the Banner Rotator but nothing seemed to be operational.
After a bit of investigation, we noticed that our ‘Design Package/Theme’ (brim_design) was missing (–Please Select–) in the New Widget Instance->Frontend Properties –>Design Package Theme. This was occurring even though we we’re available to select it from the select drop down menu (see screenshot). After digging into the controller action for this, we discovered that underscores were being striped off in the action. Therefore, since our design package had an underscore, the Design Package was never being set on the Banner Rotator Widget.
A quick fix for this issue was to create a copy of the Design Package (ex: frontend/brim_design) , rename the folder and remove the underscore (ex: frontend/brimdesign), then change the Current Package Name in System->Configuration->Design.
It’s generally recommended that you avoid using underscores in your Design Package names and in other places throughout Magento.