Crashes when attempting to load "Episode 2"

[FeisarX]

When selecting "Episode 2" the game closes and I get the following message :

Unable to load manifest file 'scripts/surfaceproperties_manifest.txt'

I don't know if this matters - but I can recall I actually purchased this game on CD's back when it launched. Any help on this is appreciated.

Note : I tried the beta version as well. No dice.

[Rick Sanchez]

I guess you have to restart your pc and try again some people are having problems with verifying their files too (same for me) after the update ı dont know much sorry it says 10 files failed to validate even after Reinstalling it or verifying the files again same thing happens gotta wait for valve to fix it ı hope so of course