The mods I have are:

• Nraas Story Progression Mods (Base and all)
• Nraas Woohooer mods
• The rest are all aesthetic mods (hair, eyes, etc)

Everything was going fine until I stupidly updated Sims 3. When I loaded my save, everything seemed fine- a bit of lag, but fine. Then it crashed. I supposed that my current 1.50 patch was the cause so I replaced the Nraas mods with the 1.50 versions. When I came back to my save, my sims were missing their avatar pics, time went on, but everything else froze. Also, the Woohooer base mod seemed to be detected as an error, so I deleted all the woohooer mods and I still get the same result.

So in other words, I don't know what's the problem. Should I just make a clean save and then slowly add all the mods back?

EDIT : Ok, I found the solution. It was as easy as deleting all the mods and then slowly add the mods back. Now there are no problems... except one lot having sims' needs never decrease (which is fun, but gets too easy) yet another lot has sims' needs decreasing slowly and recover naturally.

That would be a good place to start I think. Remove all mods, see how the game runs on its own, if it's fine, slowly add the mods back one by one.

And if you're still stuck after doing that, mosey on over to the Sims 3 Help section, where we've got troubleshooting FAQs and a QA forum.

One thing's for sure, never start a game with mods that aren't your patch level. That's why patching is not something you'd do in five minutes.

Remove cache files from my documents folder!!! They all look like (something)Cache.package.

Before I've learned that I used to have many problems after updating game and mods.

^ What IzzyBess said. But don't delete the 'socialCache.package file. I don't know why, I've always been told not to delete that one

Try games4theworld's ultimate fix (google it), but...
For some people mods/cc don't work.
It works for me, but you can never be too sure...
Hope this helps.