@puzzlezaddictThe workaround you provided the link to did the trick for me, and I'm able to run the game without trouble. Since then, a smaller issue has come up. I've been able to reinstall the CC that I most wanted; I could live without the rest and got rid of it. But now I have a problem with installing my own house builds into the game. In the last few months I created a number of houses and uploaded them to the Exchange, and when I did, I saved the Sims3Pack files from the Export folder into a separate desktop folder. So when I got my game back up and running earlier this month, I thought it would be a simple matter to place these files into the Downloads folder and reinstall them.
Unfortunately, they don't stay installed. The launcher installs them, and they look fine; but when I go into the game, they don't show up in the saved-houses bin. If I leave the files in the Downloads folder, the next time I bring up the launcher, they show as not installed. I tried redownloading four of these builds (all without any third-party CC at all) from the Exchange, but that makes no difference. I didn't even have to go into the game; I installed them, exited the launcher to delete cache files, restarted the launcher, and saw those four builds showing up as not installed. This happens only with my builds, no others. The only way I've been able to save these houses into game memory is to do it from save games in which I placed them on lots. I haven't used all my builds in saves, so I've been able to save only about half my builds like this. Is there a fix to the installation problem, or will I need to find another workaround? It's just occurred to me that it might work if I try extracting the package files and putting them in that way, but I haven't had a chance to try this out. But this problem is weird enough to make me curious as to what might be the cause. Thank you again for your time!