Steps to reproduce: 1. Try to visit a host that doesn't respond on port 80. I first tried it on a registered domain name where the server was down, but I've also reproduced the problem with http://10.20.30.40 (not defined on my network) and 188.8.131.52 (not currently responding, I don't know if it ever works). 2. Wait for the "The connection has timed out" ... message with a "Try Again" message. 3. No, I've changed my mind. Don't waste your time sitting and waiting, go do something useful and come back later. 4. Back and have the message? Good. Click the "Try Again" button. 5. Press Control-T and Control-N. Step 5 should create a new tab and a new window, but neither the tab or window is created. Setting focus to the URL bar or clicking on the page will allow control-T and control-N to work, but that step shouldn't be necessary.
Confirmed on Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:11.0a1) Gecko/20111212 Firefox/11.0a1 ID:20111212031122 Control-T and Control-N don't work while the tab is "Connecting..." after pressing "Try Again", both are functional once "The connection has timed out" re-appears. Control-T and Control-N work if "The connection has timed out" tab it's refreshed (F5).
wfm on Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:29.0) Gecko/20100101 Firefox/29.0 Can you please re-test on your machine?
I tested on Ubuntu and Windows 7, control-T and control-N both work correctly with today's nightly.