Hi Jess,
Here's something that might help with the invisible Sims bug.
Crinrict's Blog - Invisible Sims
http://sims3.crinrict.com/en/2011/04/bug-invisible-sims.htmlAs for Create A Sim not loading. You may want to try some of these tips, if you haven't already.
Delete the cache files (socialCache.package, Sims3Logs.xml, simCompositorCache.package, scriptCache.package, compositorCache.package, CasPartCache.package)
-- and delete everything except Ccmerged.package file in your DCBackup folder.
-- Documents > Electronic Arts > The Sims 3 > DCBackup
If you've got mods and custom content, regardless of if it's items made by EA or 3rd party CC, try playing without them to see if that helps. Copy your mods folder if you have one to the desktop. Load the launcher, click the Installed Content tab, and checkmark Run without custom content.
Try a factory reset - Copy your Sims 3 folder to the desktop. Rename your current Sims 3 folder to something like Sims 3 Current. Click the Sims 3 icon to create a new Sims 3 folder. Then copy your game saves, files and such over to the new game to see if that helps. (This is different from a total-game reinstall)
If you find that none of the above help, please post back so we maybe able to help further.
MrsFlynn