Hi Thissucks24. You have a couple of options, given that this error typically means you have outdated/broken content in your Mods folder. One is to check at the mod creators' sites for updates or reports that mods are broken. You might catch the problem that way.
Another option is to do a 50-50 on your Mods folder. This means organizing the files there into bite-size batches and testing one batch at a time. For each test, delete the file called localthumbcache, then put only that batch in Mods. If your game opens, set that batch aside as "cleared" and delete localthumbcache again. If it doesn't open, take out half the batch and see if you're closer to finding the culprit. Remember to delete localthumbcache each time. You'll find some 50-50 method tutorials online too. Once you isolate the file, you can go find out if it was Sims 3 CC or if there's an updated version.