Re: error code it is recommend that you relaunch your game?!
@Rotblut Tools like CCleaner can absolutely delete important files as well, including but not limited to when they flag multiple, individually necessary, versions of a given file as duplicates and remove one. CCleaner is very useful if you know exactly what you want removed, but otherwise it's not a great idea to run a sweep just for fun.
And again, this particular error is an in-game issue: depending on the error code, it's a corrupt save, a corrupt sim or lot within a save, bad mods or custom content, a known bug, or some combination. It is not a system issue, and CCleaner will do nothing to address it.