I'm having the very same issue with the click fridge to cook together with another sim and the game froze with the grey-ish screen today and it won't let me click on anything. P.S. I have no MODS installed and this is a clean save, I just started it.
Not sure if this helps but it seems the grey-ish screen is when the menu needs to pop up to choose what to cook and it's not popping up and the game just sits there frozen.
It happend to me too, never with fridge but mostly when I order dyes for fabricator or if I want to travel somewhere by the phone, always when speed of my game is fast. I didnt know for first how to save my progression so I had to quit the game and when I came back so my save it never happend again in same situations.I was quite desperate about my lost progression so if anybody has same problem - I click on windows key on keyboard, then click down with right mouse bottom on icon of Sims game and click on "close window". Window is not closed for real, I go back to game and it will automatically ask me if I want to just quit or if I want to quit and save the game. I know it is not solution for problem here but at least you can save your progression, so it might help somebody.
This actually works on with Alt + F4, then the save window also appears. ^^
