Safari incorrectly demands to select an SSL client certificate Several websites suddenly recently have popped up the dialog sheet in Safari requesting me to select an SSL client certificate. None of these sites (one example is forums.macrumors.com) actually use client certificates at all. It doesn't matter which one I pick, the dialog simply comes back. If I select cancel, then loading the site simply hangs.

None of this happens with any other browser, or with Safari on any other machine.

Where do I aim the scalpel to chop out this particular cancer?

Among the things I've tried... Looking at the console app, looking at the console in Safari (I simply get a message that loading failed because the site requires a client cert - which is wrong), disabling all extensions, deleting all website data.
We were having this problem on our site with Safari users on a mac/macbook (iOS was okay).

On our server (Apache) we commented out two optional parameters in the httpd 'conf' file: SSLVerifyClient and SSLVerifyDepth. Our SSLVerifyClient was set to 'optional' which seems to be the issue. The default is "none" and I believe not commenting out the SSLVerifyDepth creates problems as well.