Hi 'oudeheer'  !

Weird ....... unless : Do you have the same security and/or anti-virus software on both devices  ?

yes, both devices are quite similar (and up-to-date). Accounts are administrator. Antivirus is only Defender. First question is: is musico.nl properly configured? (site is truthworthy, no point). Has it something to do with ipv4 or ipv6? Of course, I can overrule the warning, but still the different behaviour between PC1 and PC2 amazes me.

oudeheer said

Has it something to do with ipv4 or ipv6?

You could check the setting in about:config on both devices and see if they have the same value for the preference network.dns.disbaleIPv6

Of course, I can overrule the warning, but still the different behaviour between PC1 and PC2 amazes me.

Same here .... What's the exact message that you get  ?

I checked network.dns.disableIPv6; both devices same (default, boolean, false). I checked network adapters: both the same settings (IPv6 checked). I thought: maybe the encryption used (256 bit). I tried Rabobank.nl with same encryption: no problem with this site. I cleared all memory in Firefox: no effect see also: image provided

oudeheer said

see also: image provided

Under the Security tab => verified by, your screenshot shows : 'not specified' (hence the 'insecure connection')

'My' musico.nl says : verified by 'COMODO CA Limited'

Do you get the same on the other device ( 'COMODO CA Limited')  ?

Oops .....

PC with insecure message image 1: main page image 2: general tab image 3: media tab image given earlier: security tab

PC without difficulty main page is the Musico page image 22: general tab image 44: security tab With this PC I see more tabs in info window

I did check the internet options in the control panel No major differences.

This article explains what the message means :

What does "Your connection is not secure" mean  ?

But that does not explain why this happens on one device and not on the other. I'm baffled ......

I can only hope that somebody else will see this and comes up with a sensible explanation.

Just one more question, though :

Does this happen with Firefox only, or with IE as well  ???

And another :

Are time and date on both devices correct  ?

Only Firefox. IE on both machines no problem.

Time and date are the same. Both PC's are on the same router.

I am baffled too.

jongeman (lol) In fact there are two questions; 1 who do two PC's, quite similar and connected to the same router, behave differently? 2 what is special to this Website whereas other websites donot give this effect?

I am still thinking about IPv6 and dns problems. I will investigate further tomorrow. It would help me how I can find out with IE or Firefox, and a Website, whether it is an IPv6 or an IPv4 connection.

Wanted to save you the trouble and did this :

Problem seems to be solved. It is not related to firefox. It is not related to Musico.nl It is also not related to the following: The dns server of our provider doesnot provide an IPv6 number for the Musico site. Therefore on both PC's we have an IPv4 connection with Musico (other Websites may have an IPv6 connection, so both PC's can handle that).

It was related to a faulty PC. I newly installed this PC with a Macrium image of some month ago. What appeared: no error message anymore with the Musico site! The only real thing what happened between that image and the present situation was a registry cleaning with CCleaner (version 5.23, not the present one with malware). I never had problems before with CCleaner, but now I hesitate to use it.

Thanks for your help and I consider the case as solved.

Thank you for letting us know   !

By the way : CCleaner has proven to be a major pain in the toosh ......

You mentioned not having any security and/or anti-virus software installed : well, good for you  ! Venting my personal opinion : With Windows' built-in Defender and the best browser on the planet, it's like being in Fort Knox  !

Also see : http://tech.firstpost.com/news-analysis/ex-mozilla-firefox-developer-says-anti-virus-software-does-more-harm-than-good-359798.html

The doesn't send all intermediate certificates needed to build a complete certificate chain.

• https://www.ssllabs.com/ssltest/analyze.html?d=musico.nl

A server needs to send the full certificate chain that includes all required intermediate certificates. Firefox automatically stores intermediate certificates that servers send in the Certificate Manager for future use, so if you have visited a website that has send this intermediate certificate in the past then Firefox will not display the error page when you visit a server that doesn't send this intermediate certificate.

If you visit a server that doesn't send a full certificate chain then you will only get an untrusted error if Firefox hasn't yet stored this intermediate certificate because you have visited a server in the past that has send this certificate, but you do get an untrusted error if this intermediate certificate isn't stored yet.

oudeheer said

Problem seems to be solved. It is not related to firefox. It is not related to Musico.nl It is also not related to the following: The dns server of our provider doesnot provide an IPv6 number for the Musico site. Therefore on both PC's we have an IPv4 connection with Musico (other Websites may have an IPv6 connection, so both PC's can handle that).

Apparantly you haven't looked at my screenshot ...... But that's neither here nor there, as the culprit was your PC, which makes perfect sense.