readydlna v4.2.22 & v1.0.25 scan in progress stuck

Hi: having spent a proportion of my Christmas holiday trying to tame my set-up (Duo v1, WDTV Live, Bravia TV etc) I've become aware I have a similar problem: previously I've been accessing files on the Duo via a 'network share' login on the WDTV- this has always worked fine, and stil does.

However, when trying to use the DLNA server, the media scan stops on encountering files larger than a certain size- I have some sizable Blu-ray rips in mp4 and mkv format (these files play fine), and it appears that the scan halts on encountering any file of about 5 gig in size or greater. As the scan progresses no further, the service never gets as far as scanning my music collection folder, and thus the NAS is useless when called on to act as a DLNA server.

Any clues? I'd be keen to try the downgrade and re-scan option that some have had success with: can anyone point me in the right direction of the best OS/ DLNA version to use for an original Duo?