Comment 5 for bug 14576

Sending to Networking. This messes up the browser, too: if an alert is
displayed in one window, clicking on links in another window doesn't work.
Once I dismiss the alert in the first window, the throbber starts animating and
the link loads. (Fwiw, the alert in the first window doesn't block me from
navigating session history in the second window.)

I found several bugs that look related, but they're all linux-only:
 bug 61590 Modal "OK" warning windows eat CPU - see trace
 bug 56978 alert dialog consumes 100% cpu if network is down
 bug 65521 modal dialogs should only freeze parent window (not all windows)