Two things to try first, one at a time:
1) Go to My Documents--EA Games--The Sims 2 and delete the file named groups.cache -- this is perfectly safe to delete, and the game will create a fresh file.
Then launch the game and see if the 'hood runs any better. If things are tip-top, then ignore step 2 below.
2) Go to My Documents--EA Games--The Sims 2 and temporarily move the folder there named Downloads to someplace else on your computer (DO NOT delete this file, just move it).
Then launch the game and see if things are better. Don't Save the game after testing, just Quit the game.
If the problem still exists, then move the Downloads folder back to its original location.
However, if step 2 has helped, then you have custom content or hacks in your Downloads folder which are either in conflict or which are incompatible with the game(s) you have installed.
You'll have to move the Downloads folder back where it belongs and go through your custom content to find the culprit(s). Time consuming, but tried and true method for ferreting out the problem file(s) is the 50 per cent method:
http://www.sims2wiki.info/wiki.php?title=Game_Help:Finding_Problem_Custom_Content#The_50.25_Method