Since January 26, 2018, when I Ctrl+click a link or select "Open link in new tab" from the right-click menu, the new tab opens but then it closes immediately. It also happens with "open link in new window". The same thing happens when I click a link in a webpage that's configured to open all links in new tabs -- but not always. When I click the tab bar plus sign, the new tab always opens without problems. Likewise, File > Open [new whatever] always works. I'm running Windows 7 SP1. The problem coincides with the automatic upgrade to Firefox 58.0 (64-bit). I haven't changed any computer or browser settings recently. Can anyone suggest troubleshooting steps for this problem?