I can't speak for TwonkyMedia, however some users here have posted on the forums that breaking large files into two smaller files solves some incompatibility issues. I'm not sure if that's the solution you're looking for, but maybe an option to consider.
I'm suffering issues with my new UE32C6620 Samsung TV connected via DLNA to a Thescus N3200PRO running TwonkyMedia 6.0.
All are running current firmware, the media server is TwonkyMedia 6.0 (I have also tried RC3 but to no avail).
The issue is when attempting to play a large M4V file (1.8Gb) the TV will sit saying "loading" for about a minute and then suddenly reboot/restart.
Has anyone else seen a similar problem / have any ideas on how to resolve this.
It certainly looks like a Twonky/Samsung issue, as it can run fine using Mediatomb. Would prefer to use Twonky though as I'm not a linux expert and am unable to create/install the script to autostart this daemonised on my NAS.
Any help would be gratefully received!