Since 2 or 3 days it's impossible to open websites. Each time I try to open a website (saved website) I receive the error message "PR_END_OF_FILE_ERROR", due to a security problem. According to Firefox the website (page) can not be opened because the authenticity can not be verified. It is a very strange situation, because this problem came out of the blue. The websites I'm trying to open, are saved websites without security problems so far. Moreover this strange situation is only occurring on my "desktop pc with Windows 10" and does not occur on my "laptop with Windows 11"! More important info: the problem is occurring with an ethernet connection both with a WiFi connection. My laptop is always connected with a WiFi connection. Both devices do not use VPN. On both devices is running Bitdefender (with exactly the same options), CCleaner/Kamo (of CCleaner, with exactly the same options). My service provider is Ziggo Netherlands. Consulting Internet, I tried to fix this problem by applying a lot of adviced changes into a lot of options. All without any success. One of the advices I did not try, is turning off the virus scanner Bitdefender, because I do not know how to turn off and how to again on. I did turn off Bitdefender firewall, without success. Fyi: I always use Firefox and I never use Chrome or any other browser. However I checked the situation with Chrome and to my surprise, the same website connection problems did occur! Please advise how to resolve this problem. Thanks in advance. Best regards, Peter