Follow along with the video below to see how to install our site as a web app on your home screen.
Note: this_feature_currently_requires_accessing_site_using_safari
Have you tried verifying your game cache in Steam?
Right click Episode 2 in steam, properties, local files, verify integrity of game cache.
Did you play it with the new client or only with the old?
> http://forums.filefront.com/hl2-problems-errors-help/184983-failed-load-launcher-dll-solved.html
If that didn't help, you must reinstall HL2:EP2 (take a backup of your config)
btw: what Windows version are you using?
This is all Valve have on the subject:
https://support.steampowered.com/kb_article.php?ref=6897-DMYX-9004
So try going into your game files and deleting the 'Bin' folder.