I delete every single file that isn't a folder in my Sims 3 Documents directory. Like, in My Documents/The Sims 3. All the caches, but ESPECIALLY any xcpt files. Those fuck shit up bad.
I've just spent the last two weeks designing a neighborhood from scratch too. Not even done. I can't even imagine your pain.
Did you build the worlds yourself too, or just the neighborhood? If you want you can send me your neighborhood and I can test it on my computer. I play with a Mac, and our game issues tend to be worlds apart from the PC world so who knows.
It only won't load this neighborhood when you play with the witch, or anyone in the town?
You can harass EA, I did recently - although their help is notoriously a piece of shit and I did just get copy pasta about custom content despite specifying there was none installed. They're especially bad with Mac inquiries though, so it may be worth a shot. Otherwise I hope you've googled the hell out of this already, I can't tell you how valuable that's been to me because EA can't make a working videogame to save their lives.
I guess I'm lucky enough mine loads, but it fucking HATES create a sim. And I'm a fickle player, I don't care about advancing my Sims as much as I do constantly tweaking their looks and re-designing all the NPC sims. But it loves to bug the fuck out and plain crash half way through it, sick of having to save Sims 10 times over before they get finished. It's been happening since a recent patch, a newer one didn't fix it and EA probably wouldn't give a shit anyway, they already got their money from me.
EA never gives a shit about their Sims glitches or players.
Besides that, I hear that their tech people/coders/whatever you call them have to work a 90 hour work week. The stress level of their coders must be insane, not to mention the lack of sleep. I've heard other companies will refuse to hire you if you worked for EA just because of how much of a mess you are when you come out.
It does EVERYTHING. Here I will fetch a link for you.
It's hard to summarize. I use the custom-set awesome mod configuration, and I would suggest you do too as it's pretty awesome on it's own but I like to take it to the next level, and there's some settings I like to de-select and others I prefer to enable.
To summarize, it fixes story mode, makes a better name generation, adds more detailed stats of all items, etc. With the configuration tool you can use it to remove sparkles, show naked sims, increase the max family size, make NPCS change out of their work clothes when not at work, make households that aren't active stop aging/pay bills/eligible for promotions at work/earn lifetime rewards, stop them from constantly reading Raymundo, more precise times for moodlets, can stop recipe books from disappearing once read, smarter chair-finding, "wire house with speakers" no longer in bedrooms, grow plants on any lot, sim-written books sold at bookstore, keep marriage lines on family trees...
Seriously the list is huge, I just picked random favorites of mine, I have no idea what is more your style but if you browse the config page you'll see everything it can do. You need to save both awesome.package and the one generated by the configuration page together with all your other package files. Only rule is it's the only major mod of it's kind that can be installed at a time, although a no-CD or no-intro mod is not major and will work fine with it.
Did you update your game in between each expansion pack you installed? Installing everything in one go and then updating fucked up my game real bad. Honestly? Every time I take a two month pause on playing the Sims for school, when I get back they've done SOMETHING and I have to do a fresh install. EVERY. SINGLE. TIME.
This is my first time in the Sims series that I bought the base game and EPs rather than pirating. Never again, EA. Cracked copies work better.