First off you are able to save and load your game after todays update. Make sure that "hm_Data/SaveStates" directory is created after game is updated. Yep - luck of that folder caused all problems.
In case of Mac build let me quote our technical team member:
"Files downloaded by steam as a game are simply nothing. OSX build is uploaded but client is not downloading correct files. Strange thing is that on developer account it works. I need some more time to fix this. I am realy sorry for that. It is late sunday night now in Poland so let me fix it tomorow. Thank you for your patience."
We wrote e-mail to our Steam Technical Manager - hope he will be able to help.