Do you have any custom content installed??
If you have hacks or some custom careers in the game this scan cause this to happen
If you do have downloads added I would get the Clean installer and run it and remove any hacks or mods.
Also a good tip Always put hacks in a sub folder inside the downloads folder that way you can cut and paste the hacks folder to desktop when installing a new EP and you will not likely have issues
Also Houses installed can Sometimes have hacks in them so be Careful installing
I tests all new houses in a separate Windows XP account to be Sure there is nothing sneaking in So far I have had No problems well I had ONE crash when a creator SWORE the house had nothing and I installed without checking it and it crashed I did a scan with clean installer sure enough a hack was in it i removed it all played fine No more crashes.
So even if you did not add any hacks If you added a downloaded house You may still have hacks So a scan with it can help
You can get it here
http://sims2pack.modthesims2.com/