User Agent: Mozilla/5.0 (Windows NT 6.0; WOW64; rv:17.0) Gecko/20100101 Firefox/17.0 Build ID: 20121128204232 Steps to reproduce: clicked on tab bar [+] to open a new tab, but no new tab opens. tried opening new tab from menu bar/file but still can't open a new tab. Actual results: no new tab opened Expected results: new tab should have opened.
Please contact the support (http://support.mozilla.org) for such basic issues that are unlikely a bug. http://support.mozilla.org/en-US/kb/Safe+Mode is also a good start because this is very likely caused by an Extension. Disable the extensions one by one in tools/addons/extensions if it works in the safemode