I have tackled your questions piece by piece trying not to overlook anything. My responses are broken down below~
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2) Took out Lot Catalog
Result ~ Lots were normal - but how come those downloaded lots were still showing up if I took them out?
Showing up in your neighborhood? This is because when you plopped lots from the catalog onto your neighborhood, a copy of it was placed into that neighborhood's neighborhood folder (N00#/G00# etc)
Questions before doing anything:
So, its got to be the downloaded lots, then?
That would be a logical conclusion, but my first gut instinct when I saw your post of 'flashing red and black' was a graphics issue.
If I rid of these specific lots, will I also rid of the CC that came with them or is that CC safe because its already downloaded?
Your CC is safe, it was installed separately to your downloads folder.
I haven't downloaded lots for a half a year.
So wait, you did not install a lot recently? What was the very last thing you did before this problem started occuring? (A new EP? New hardware? Any changes to your game or computer itself...)
What I have done:
1) Removed all CC downloads
2) Played with a family I had never played before in a neighbourhood I never play in. Built and bought things for the house, waited to see if the game would do the same thing (in increments of 20 minutes), and played around with flipping through catalogs in different categories. Slowly added more CC and repeated this.
Result?
Am I doing the right thing? Could this be a CC problem if items on my screen including the tool bar blackens (sometimes my whole tool bar so I can't see what tab I'm hitting), and if words aren't even readable or is this something completely different (because removing CC has seemed to help)? Can bad CC really effect the entire screen and tool bar like that?
I tend to associate flashing red or black with a graphics issue, which may or may not be CC related. Have you perhaps installed any mods, such as lighting mods, which do not get installed in the CC folder? I once tried to install a lighting mod with an incompatible version of the game and it made my game flash RED.
Pleasantview has been giving me an increasing amount of problems. About a year ago, I had problems with Sims interacting. A couple of Sims could interact with others but others couldn't respond to them at all. I had to get rid of them. Now, the flashing lots in Pleasantview's downtown is starting to happen. What in the world could this be? Could it be some kind of bug in Pleasantview? I'm not going to have to just void this neighbourhood altogether, am I?
Is Pleasantview the only neighborhood affected?
Here are some things you might want to do.
*If you have any lighting mods, remove them.
*Verify that your video card is compatible with the game and that you have the most current drivers for your card.
*Is your computer running hot? Since things are blacking out over time and not immediately, it suggests to me you may be having a hardware failure somewhere.
Has anyone else had problems with just one neighbourhood?
Oh, it's only Pleasantview that is like this? No other neighborhoods affected? Perhaps Pleasantview became corrupt somehow :x
These are my best guesses on how to help diagnose your problems. You've already taken some good first steps! I'm not a technical expert, but hopefully my advise will be of some use ._.;