I thought I'd finally start a thread just for this problem of mine - I have described the different stages in my story thread, a showtime thread, and briefly in a mods thread.
I play with an entire neighbourhood. I turn story progression and aging off. I've documented this through my story 'The (Ordinary) Lives of Barnacle Bay' - see the link in my signature. A few months ago my game froze and would freeze every time I reloaded it. I thought that the file was too big, so I then split the neighbourhood into 2, and moved half to Union Cove, and half to Lunar Lakes. I played for about 16-20 sim days in Union Cove like normal, then it froze again. It froze on the same family that it froze with the last time (in Barnacle Bay) so I decided it must be something wrong with that family. I reverted to an earlier save (still in Union Cove), got rid of that family (Fang) and moved the Lunar Lakes half back in (as splitting the town didn't seem to have made much difference and I was bored with LL anyway). I started playing again, but it's been 1 (normal) day (or less even) and it's freezing again. I have today added both twallan's Error Trap and Overwatch, but it doesn't seem to have helped. I have tried a complete reinstall, a factory reset, and a few deletions of dcbackup and compositor cache files. The latter seemed to work once, but has made no difference since.
When it freezes, it usually happens very soon after opening the saved game, and the page freezes and I can't click anything. The only thing I can do is press Ctrl Alt Delete which takes me to task manager, and sims comes up as having a 'problem' and asks to be shut down.
I am quite miserable about all this. I have been trying to fix this for so long, gone through a few different theories to no (permanent) avail. This is the only file I want to play on sims - without this I don't want to play sims at all (because I love the story-making and the multiple families - one family is just boring). I don't know what else to do to fix this. I'm just hoping that maybe someone here can help? Or maybe I should even contact EA or go on the official forums... I am desperate.