undefined method for Polymorphic association using Searchlogic

I am unable to call a polymorphic scope using the searchlogic plugin
as it keeps on returning 'undefined method'. I am certain it is only a
problem within my project as I created a test project and I was able
to call a polymorphic scope using the searchlogic plugin.

I am hoping someone can provide a suggestion on how to debug this
issue.

My project consists of several gems, and is using Rails v2.3.4 and the
latest searchlogic repository.

Thanks in advance.

Polymorphic model association