Same problem and LG are a pain out of warranty as I bought mine on eBay. Horrible service considering this is likely down to a failed driver in the update or something thats not fixable your self once the update is applied, I've opened mine and re-connected the connections and can't see any issues / water damaged (not that i suspected any). It's put me off LG products completely.
Any tips for what to check if the touchscreen turns on but is non-responsive ?