I installed UK & NI maps ver 8.50_2520. TT one (ver 2) starts fine but I cannot go into postal code - TT freezes. I am using latest postal codes zip as well. The old 8.45 which was working ok is not working for the postal codes now.
I'm guessing you mean UKROI-850.2820 not 850.2850 but you don't mention which particular navcore you're using but , assuming, it's 7.9something you shouldn't have any problems unless you were unlucky and managed to grab a corrupted copy of the 850 Zip file or a dodgy map. Easiest way to check is re-load your backup (don't say you haven't got one!) and then throw your 850 zip file in as well and if it works then you know the zip's fine!