As this could be used as a search help for other steam users have the same issue, here is the solution to this Problem with steam update and game data:
Steam has had a couple of issues and for a few people not fully removed files that it should have and people have gotten mixed up versions of files in their game and its caused problems like this. You have to do a very clean install Its really important to do all these steps. First if you have an singleplayer saved games go to your steamlibrary common/Eco/Eco_data/Server/Stoarge and save the worlds there bith the .eco and .db files. then right click on Eco in steam and do an uninstall. Then shut steam down and go back to steamlibrary common.and delete anything of Eco left behind. Then yo to appdata/LocalLow/Strange Loop Games/ and delete the Eco folder. Then start steam back up and install Eco.
[HINT: appdata is in your Users directory usually like Users/<machine name>/appdata its a hidden directory so you will have to tell windows to let you see it]
That should, hopefully get you a working version. You may ahve to double check that Eco is still listed in your firewall and in your AV program as an exception