There was a bug in SVN which should be fixed now SVN 11104 or later.
DMAN
It's unlikely a MediaPortal issue if these channels are not found as the same BDA engine that tuned your FireDTV is used with the Twinhan so the only difference is the hardware tuner or BDA drivers on that card and what it reports back to MediaPortal.
My suggestion - edit the 19degreesEast.tpl file and remove the unnecessary transponders only leaving the ones relevant to your subscription - then re-scan and see how you get on.
DMAN
satname=Astra 1C/1E/1F/1G/1H/2C (19,2°E)
12343,H,27500
12551,V,22000
12574,H,22000
12669,V,22000