Yes, Enfold does work in Adobe Illustrator CS 5 and CS 5.1 (5.1 is part of the CS 5.5 Suite). Enfold 3D CX is an Illustrator plug-in.
An updated installer version (Enfold 3D CX 1.0.572) has been posted. It can be found in the Free Updates section of Strata.com Support pages: