There are several possibilities that exist with your WinRar malfunction. Here are some ideas...open your winrar program, and go through your settings options specifing what the program should do thoroughly. Winrar has issues with drag & drop, if you have been using this method, stop, as it causes temp file problems. If you you have recently tried to view the files with a different program other than Winrar, that too causes issues with temp files, as now Winrar doesnt think it should delete the temps. Usually by closing WinRar for at least an hour wipes the temps when restarted.
The sudden change is what is troubling. It is possible that you may may have corrupted the winrar program with a virus or malware, and it has found its way into the temp files making them undeletable by WinRar. The temp folders are in Users/ /local/appdata/temp, if you cannot manually delete any files inside, or if it states "the files are in use by another program" you have found a potential reason why WinRar has changed its behavior. Restart PC and try again. In WinRar settings you could enable error logging to further diagnose the issue.
Ive focused on these issues because the "Settings" under "Options" should have never changed on their own considering you were able click in the WinRar to view files previously. In the meantime install Malwarebytes Free and run a full scan.
Best i can do at this point.