Sims 3 64-bit: problems installing store/custom content

Marked as a solution for visibility

For anyone still having issues installing store or custom content, the update today (November 9) has fixed the underlying problem that is the most common cause of an "Error downloading content" or "critical system failure."

If you have this issue, please repair the game in Origin: open your game library, right-click on the Sims 3 icon, and select Repair.  Then open the launcher and see whether the base game icon in the lower left corner is grayed out.  If it's now green, the underlying issue should be solved, and you should be able to install content again.

Although the underlying cause of expansion and stuff pack icons being grayed out is the same, that is not addressed in this fix.  However, the grayed out pack icons should not affect your ability to install or use store or custom content.

If you still get the same errors when downloading or installing content, and your base game icon is NOT grayed out in the launcher, please move the entire Sims 3 folder out of Documents/Electronic Arts and onto your desktop, open the launcher to spawn a clean folder, and download a fresh copy of one item to test.