I am working on developing a managed package (Package A) that integrates with a another managed package downloaded form the AppExchange (Package B). By integrate I mean, creating VF pages with the controller that is from Package B and an extension from Package A.
I am doing all this in the packaging org, i.e. the dev org where I am creating managed package A.
On page load everything is fine, however when I call a action method from the page I get Apex class not found error. E.g.
Apex class 'packageB_namespace.PackageA_Class' does not exist.