Firefox issue

I’m using Firefox v 11.0 on Windows 10.

New issue today: if I click on a thread in the LR, it opens in the same tab. If though I right click on the same thread and try to open it in a new tab, I get a new tab labelled Oops - Error 500, and in the new tab:

Oops

The software powering this discussion forum encountered an unexpected problem. We apologize for the inconvenience.

Detailed information about the error was logged, and an automatic notification generated. We’ll take a look at it.

No further action is necessary. However, if the error condition persists, you can provide additional detail, including steps to reproduce the error, by posting a discussion topic in the site’s feedback category.

None of these are private tabs.