Move the CC you just downloaded out of your Mods folder. You can create a new folder on your desktop for the moment and just put the CC in there. Then start your game again and see if it works. If the game works, then one of the files you downloaded is corrupt or may be for TS2. Try adding the CC back one file at a time until you discover the one that is giving you an issue.
You can also download delphy's package cleaner to search your mods folder for corrupt items. If the CC is Sims packs, you can download delphy's sims3pack cleaner and run each pack individually.
