What are the error messages you are getting? If they are Sims 2 errors- the debugging errors- then this has nothing to do with your hardware and is caused by game errors (custom conflict errors usually). If they are Windows errors, then it could be software or hardware depending on the error. You'd have to give us some more info to be sure.

Do you have another computer with the same graphics slot that you can swap cards with? That way you can determine if it's the card or the mainboard.

Aww, this is really sweet! What a great idea. Thanks! And, I love your Llama avatar too.

But don't subfolder them for basegame only. Also you should make sure that Downloads has a capital D and SavedSims has capital Ss. If in doubt, run bodyshop, create a sim and import it into the game so that you have Downloads and SavedSims folders created for you.

Sounds like you still have conflicting CC; uninstalling won'y help unless you also delete your CC (and it would be quicker to just delete the CC!). If you want to find the problem file you could do this:
http://www.modthesims2.com/wiki.php?title=Game_Help:Finding_Problem_Custom_Content
Also you could attach an error log for us to look at which may narrow things down a bit.

Yes, in the error log the job is listed as being called 'Singer'.

Yes, Jenna has it.
Also, this may help:
http://www.modthesims2.com/wiki.php?title=Game_Help:Finding_Problem_Custom_Content
If you do have any files in your Saved Sims folder, you would probably find it easier to put them into the Downloads folder whilst you do the binary search.

If that fails you could try a manual local install:
EA Help

This may help too- also, run Bodyshop to generate a clean Downloads folder:
http://www.modthesims2.com/wiki.php?title=Game_Help:GCCTSU

This does sound like it could be caused by custom content- most likely hacks. To test this backup your userdata files (Documents\ EA Games\ The Sims 2) and then test the game with your Downloads folder removed. If it works, you know your CC is the problem and you need to do a 'binary search' (I call it the 50% method) to find the problem file(s):
http://www.sims2wiki.info/wiki.php?title=Game_Help:Finding_Problem_Custom_Content

No, you can go ahead and install all of the patches at any time. Remember to backup your userdata first. If the patches fail with a note that you should reinstall, just do this:
http://www.sims2wiki.info/wiki.php?title=Game_Help:Game_Patch_Issues

Can you raise the camera by using the Q and E keys?

I had a similar thing:

The only way you'll find it really is by doing a binary search. Don't forget to check the Saved Sims folder too- in case you have packages there too.

If it is just with this sim, try turning on moveobjects and deleting her. Save, exit then re-enter lot. This will reset her. Maybe that'll help?

It's the one that looks a bit like a lock in the business tool panel. You'll know when you've found it as the cars will appear in the catalog when you have it active.